put simple_rng methods in own file.
add new rng

the plan is to have random_new::generator which can be a rng_synced or not dependng on whether we are in a synced context (for example select events are no synced context)

this commit is part of pr 121.
add replay_helper class

the main intention was to make the file replay.cpp smaller during writing pr 121.
also in order to use synced_context::run_in_synced_context this is useful.
(replay_helper.cpp was already accidently moved into makelist.txt in a pevious commit (add new rng))
add config_of function

in the file config_assign.cpp/hpp, it can be use similar to boost's boost::assign for config object.
I don't use it that much, but i found it useful especialy to pass or return a config that just contains one or two childs.
add functions in replay

these will be used in synced_context.cpp.

this commit is part of pr 121.
Minor code cleanup.
Optionally save an SDL_Surface when loading a texture from file.
Allow streaming access for textures loaded from file.
Properly clean up source_surface_ for streaming textures.
add synced_context class

the intention  is to fix #20871 and implement #21697, to sync
prestart/start events, and to implement
http://forums.wesnoth.org/viewtopic.php?f=6&t=39611 in the next patches,

the intention of synced_checkup is to replace random .. set/get_random_results.
Because set/get_random_results didn't have much to do with random, since it was only used to compare unit checksums and attacker damage to replays.

the intention of synced_commands is to move code out of do_replay_handle and make it callable from other places too so that we can just call the same function taht was called from replay in the simple cases (with synced_context::run_in_synced_command).

the object set_scontext_synced can be used to enter the synced context which enables synced_checkup and make the random calls synced.
Or we can use run_in_synced_context which is normaly easier than set_scontext_synced.
we can check wether we are in a synced context with get_syced_state to make addidional checks to detect oos (the other intention of that is to implement #21697 ).

this commit is part of pf 121.
give a better error message.

when a player leaves a mp game during a lua call and the other player
pressed escape, lua catches the error that should exit the game, idk
wether i can fix that but at least i can give a better error message.
use rand() instead of get_random() for side shuffle

1) i think it's better to use a simple rand function for things that are
never synced, because everyone knows that rand() isn't synced.
2) my plan is to delete the get_random() function.
fixes wrong side during end turn events in replay

this didn't matter before because turn end event weren't synced before.

this commit is part or pr 121
fix a bug when players leave in mp.

as pointed out by EliDupree:
http://www.wesnoth.org/irclogs/2014/03/%23wesnoth-dev.2014-03-19.log

init_side_done_ should be false if we wait for a init_side and true otherwise.
This fixes a bug that init side would happen twice when a player leaves durign a side turn event that uses mp_sync

this commit is part of pr 121
serverside code for the new rng.

I decided to implement the check for require_random in the client instead of the server to fix a possible OOS:
to reproduce (assume a server check like "user->first == owner_"  for require_random in the servercode):

[event]
name = "turn end"
[set_variable]
name=v1
rand= "1..8"
[/set_variable]
[/event]
[event]
name = "moveto"
[message]
side_for=2
message="adfsd"
[/message]
[set_variable]
name=v2
rand= "1..8"
[/set_variable]
[/event]

Do the following: (in a 2p scenario, with no hidden sides):
1) move side 1 leader
2) ignore the message on side 2
3) click end turn on side 1
4) then click on the message on side 2.
5) ->>OOS.

the reason is, the when the rand for v2 is executed on side 1 the
current_side on the  server is side 1 and when rand for v2 is executed
on side 2 the serversided current_side is side 2 => the server accepted
both require_random

this commit is part of pr 121.
use new synced_context: use new rng

the plan is, that random_new::generator will be a object that does synced random calls during a synced context and otherwise not,
so that we cannot create OOS anymore by using random in unsynced actions like select event

the intention is also to unfy random calls for attacks and random calls and for other actions like traits and [set_variable] rand= .

the synced random generator will be set with the set_scontext_synced object.

the new rng will be similar to the old rng used for attacks becasue it will ask the server for a new seed for every new user action (=recruit, attack...) that requires random numbers.

Previously there were 2 different random generators, one for attacks, and one for other things, pr 121 is supposed to fix the problems with the "sending data over teh network first" an we try to throw the old rng for non attack things out. So that attacks and other tings use the same rng.

We use a new random generator which is automaticly synced during the execution of scned_context::run_in_scned_context, and otherwise not. So we cannot cause oos anymore by using rand= from an unsnced command like "select"
Alternativeley we can also set the new random synced by using the new RAII object set_sconext_sycned, this happens for example during prestart events.
Unlike the old random generator, the new random generator is not determinstic by default because it asks the server (or itself in a SP game) for a new seed, at every side command (attack, move, recruit ...) that requires random, similar to how the previous rand for attacks worked (it doesn't ask at the beginning, just the first time it is needed unlinke how attacks worked before). That way i can also use the same rng for attacks and for other random choices.

I also plan to move the code from set/get_random_results to syncec_checkup.cpp later.

this commit is part of pr 121.
use synced_context: fix mp observers

with the new synced_context system, the old code would bring code in the wrong order onto the replay if we received data during get_user_choice
which now could be called during turn_info::handle_turn.

also previous code would fail to process
[turn]
[command]
[move]
x = 3,4,5
y = 4,3,3
[/move]
[/command]
[/turn]
[turn]
[command]
dependent = yes
[input]
[/input]
[/command]
[/turn]
because [input] would be processed after [move] was processed, but
[move] need [input] on the replay to work properly.
(if luas sync_choice was called from a moveto event)

this commit is part or pr 121.
use synced_context: change get_user_input

previously and afterwards there can be 2 ways an action(attack, rectuit, move...) can be executed, the first way is that the action runs on the local client, and the action is sended over the network as soon as it is completed, this happends in recruits, moves, recall, and some more. The second way is that the action is sended over the network first and is then executed on all cielents simultaniously, this happends in attack events, and similar happends in prestart/start events. This is also why mp_sync didn work in this actions before: side 2 noticed that it needs data from side 1 but side 1 did send the execeution of the action before it generated the user_input data. That's why side 2 doesnt have the user input data at this point. Previously there was one special and very bugged case when the code waited for remote input before calling get_user_choice: [get_global_variable].

This commit moves (and fixes) the "waiting" from persist_var.cpp into get_user_choice so that the caller of get_user_choice don't have to worry about it. With this we can also use get_user_choice if we already sended data over the network. And we can enable the mp_sync in attack related events and prestart events. The intention of this commit is to fix fix http://gna.org/bugs/?20871.

the plan is to sync start and prestart events, so we don't need to check for that anymore,
we also don't need to pass the rng because we can use call random_new::generator->..

this commit is part of pr 121
use synced context: sync the turn ... events and prestart events.

by using set_scontext_synced and recording brefore doing that.

we split fire_prestart and fire_preload becasue prestart runs in a synced context and fire preload not.

we also dont need recorder.pre_replay anymore becasue of the changes to the rng.

the line synced_context::run_in_synced_context("auto_shroud", replay_helper::get_auto_shroud(true));
was accidently placed in this commit and should rather be in the commit called "use synced_context in undo and rest"
this commit is part of pr 121.
use synced_context

these commit uses the synced_context in replays in and in attacks.
we also don't need to use expected_advanaments anymore, because advancements now run through get_user_choice.
Which was not posible before, because get_user_choice didn't work during attacks.

the main intention of these commits is to fix gna.org/bugs/?20871, gna.org/bugs/?21697, some OOS erros related to use of multiple
[get_global_variable] with different sides in one event.
To remove the deterministic random for traits and similar as discusssed
here http://forums.wesnoth.org/viewtopic.php?f=6&t=39611. And to sync
start end prestart events.

the file synced_commands.cpp is mosty code moved from replay.cpp with the main intention to make do_replay.cpp smaller. But also to be able to call run_in_synced_context from non replay if posible,
so that we can just use the same function syned_context::run_in_scned_context that we call during replays, but in most cases this won't be possible.

the file synced_checkup.cpp was written to replace get/set_random_results from rnadom.cpp which was used to check wether unit checksums and attacks results match the ones in the replay. And wasn't realy related to random.

We also use the new random generator which is automaticly synced during
the execution of scned_context::run_in_scned_context, and otherwise not.
So we cannot cause oos anymore by using rand= from an unsnced command
like "select"
Alternativeley we can also set the new random synced by using the new
RAII object set_sconext_sycned, this happens for example during prestart
events.
Unlike the old random generator, the new random generator is not
determinstic by default because it asks the server (or itself in a SP
game) for a new seed, at every side command (attack, move, recruit ...)
that requires random ,similar to how the previous rand for attacks
worked (it doesnt ask at the beginning, just the first time it is needed
unlinke how attacks worked before). That way we can also unify the rng
for attacks and for other random choices.

this commit breaks ai's advancement aspects, i'll bring it back in a later commit.

this commit is part of pr 121.