Update Chinese simplified translation
ChessEngine: fix minor file descriptor leaks
Remove stock items from the preferences dialog

Also, switch to a symbolic icon for the light bulb.
Don't leave an orphaned engine if we crash

If we crash or receive a signal that kills us, the chess engine might
live on forever. Linux (and only Linux) provides a nice way to avoid
this by tying the life of a child process to its parent. Use it.

(To get equivalent behavior on other systems, we would need to fork a
third process to function as a monitor, which is not worth the bother.
Non-Linux users should simply not crash the game.)
trivial: remove extra braces around lambdas
trivial: rename open_cb() to open_dialog_cb()
About dialog: update website
Remove extra translatable string

This is the default
Updated Lithuanian translation
Prepare 3.11.4
Updated Galician translations
Updated Greek translation
Updated Spanish translation
PGN: remove empty default constructor
load/save: never show uninternationalized text
Updated Traditional Chinese translation(Hong Kong and Taiwan)
Updated Czech translation
Updated Czech translation
Updated Brazilian Portuguese translation
Revert "Updated Brazilian Portuguese translation"

This reverts commit 832e8d9308026cde3a9d65f70212d2f36cfc6d44.