Qt client: Add assertions to reveal issues in the diplomat queue handling.

See patch #4498

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24473 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Introduce action probabilities and make the clients use them.

No probabilities are displayed or calculated yet.

Displaying the probability that an action will be successful was
requested by Jacob Nevins <jtn>

See patch #4500

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24474 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Play music specific to player's currently active city_style.

See patch #4490


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24475 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Combined helptext_base() and helptext_road() to one helptext_extra(). 

See patch #4494


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24476 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Enabled techlossrestore in civ2civ3 ruleset

See bug #21637


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24477 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Update screen on every round of main loop of sdl2-client

See patch #4480


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24479 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
gtk3-client does not advertise itself as able to handle .xpm.

See bug #21604


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24480 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Pass the acting diplomat from the generic to the specific client code

All packets asking follow up questions about a spy action contain the ID of
the acting diplomat. The generic client code already use it.

Change the interface between the generic and the specific client code so the
diplomat is forwarded to the client specific code. Having the real diplomat
as a parameter is useful when fixing a bug caused by a client specific way
of guessing what diplomat a follow up question refers to.

See patch #4502

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24483 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Fix capitalized of "Writing" in action enabler documentation

See patch bug #21645

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24485 a0f10bec-cc02-0410-94fc-a9cfff90b4cd