Fixed selecting of beings that are flanked between two others

Before it was a bit tricky to select the a being if there are two others around.
I fixed this by going through all sprites and looking for the closest one to the
mouse.

Reviewed-by: bjorn.
Fixed error in the German translation

Reviewed-by: Erik Schilling
Fixed manaserv-enabled builds

Wrong define was used in the code.
Added notification sound on receiving whisper

One of the sound channels is reserved for notification sounds, of which the
volume can be configured separately. Currently, the only notification sound
that is played is for receiving whispers. That can be extended later.

The newmessage.ogg sound used currently is the one for receiving a message
with the Psi instant messenger.

Parts of this patch are based on the new message notification in ManaPlus.

Reviewed-by: Erik Schilling
Fixed category of mana.desktop file

It is not allowed to provide multiple different categories since it would spam
the menu too much. openSUSE prevents packaging if a .desktop file does not
follow this rule. So I removed the Application category and added a subcategory
of the Game category.

See http://standards.freedesktop.org/menu-spec/latest/apa.html for more
information.

Reviewed-by: Bertram, jurkan.
Updated finnish translation
Fixed compiling against SDL_mixer versions before 1.2.9

Mix_LoadMUS_RW was added with SDL_mixer 1.2.9.

Reviewed-by: Erik Schilling
Updated the Brazilian Portuguese translation
Fixed display of server description

Reviewed-by: bjorn.
Removed some 'const' keywords from value returns

It makes no sense to mark a return value as const when it is returned by
value.  This only makes sense if the return value is passed by reference, in
order to prevent the receiver from modifying the value.

Also made some other small adjustments. A std::string does not need to be
initialized to "" explicitly and getSafeUtf8String could take its parameter by
reference.

Reviewed-by: Yohann Ferreira
Polish translation updated by Derpella
Merge branch '0.6'
WIP Fixed -1/+1 indexation mess around the emoticon id use.

It permitted me to remove a todo, but also to fix the last
emote in the emote popup which would never have worked otherwise.

I also Fixed the emote shortcut bar once and for all.

While on it, I made the number of available shortcuts
for the config and the bar be defined only once.
Also made it suport emotes id equals to 0.

The emotePopup window and its container, the window menu
were adding one to the emotes index in the list
and checking them to be > 0 before permitting
to send the emoteid to the server.

The nasty thing in there was that the index was incremented
by 1 when selecting, and again by one, when getting the selection,
as seen in the EmotePopup::getSelectedEmote(),
leading to the todo: //TODO: figure out why the -1 is needed
because the id sent was alway +1 of the actual requested.

Plus, as the effect id (fx in the code) was decremented,
this dirty hack prevented to have non-contiguous effect ids
for emoticons.
As for the emoteshortcut bar, the index was incremented by one also.
Thus, I simply wondered how much we were lucky before,
to see all this stuff "working" so far.

And last but not least, the last emote in the list could never have worked,
since this that the emote requested in the beinghandler
was always off by one also, leading to make the last effect id
never to be found, which made the effect id never found in its turn,
leading to no emote animation in this case.

My last concern, is that I do wonder whether older clients
will see the correct animation, because of the reasons given here.
I do think not, but I'd like to get rid of this poor implementation anyway.
We might also want to sync with 4144 about that, too,
since manaplus has an actual weight on advanced users.

+ 1st bugfix round
To be redone - Added support for dynamic sprite changes.

Now an alternate visible sprite layer can be set
when wearing problematic equipment.

I made the compound sprite class handle the alternate
sprite system as the problem is only linked to such objects.
I also turned it into a map,
to permit non contigeous layer ids.
WIP Add emote through effects support on Manaserv
(Now the client is sending an emote Id.)
WIP on permitting custom acceleration on missile particles.
Added a check for previous installations in the NSIS installer script.
Optimized the inventory drawing logic.

- Made the inventory update the item list only when necessary.
- Made the draw function only parse the item map, instead
  of trying to find each slot into this map.
- Simplified the itemContainer height computation logic by
  just looking at the itemMap size instead of checking the inventory
  last used slot each tick.
  As a consequence, the inventory scroll bar behaviour has been fixed.
- Made the "Eq." tag be translatable.
- Made other small code style and comment cleanups along the way.

This should also increase performance a little bit.

Resolves: Mana-Mantis #449