Gray out the players area when the game is finished.

This was broken since 196e02f9ad30f5708596f91ce1dcb7ad1afe88e5.
Fix mismatch declaration between struct and class
Add a missing include
Fix a file name, preventing a few strings to be translated
Fix a typo
Update po files
Update of the French translation
Update of the Czech translation, by Pavel Fric
Update of the Serbian translation, by Uroš Stefanović
Update of the Spanish translation, by Joan Montané
Update of the Catalan translation, by Joan Montané
Update of the Italian translation, by Diego De Landro
Hints: fix a bug in WordLettersHint.

The letters of a word containing digraph tiles (like the Catalan 'QU')
were sorted incorrectly. For example, "AQUIETE" was sorted as "AEEIQTU"
instead of "AEEITQU".
Note: it would be even better as "AEEIQUT", but this is a different
problem...
Hints: add missing logging
Topping: give a default empty move to the player.

This avoids a crash if the player uses hints at the first turn.
XmlWriter: avoid a division by zero