Sort the VLC translation languages alphabeticaly according to their label, and not their code, in English. The order will be broken in some other languages I guess but at least it'll be coherent the first time the user launches VLC (in English) and changes the language to use in the preferences.

Fix horrible bug in language id list (must have broken the language selection dialog for a long time)

Fixes zsh completion. Same as  [17801], didn't committed back then because it wasn't compiling on trunk.

Adds 2 scripts to make vlc the default audio/video mime-type handler on freedesktop, contributed by forum user.

if it has a DEFAULT flag on it. User overrides for
preferred language should continue to take precedence.
The current versions of MKVToolnix correctly support DEFAULT
track tag but some older versions don't. If you want to have
subtitle streams in your mkv file, but not have them activate
by default, try remuxing any files causing you trouble, with
the current version of MKVToolnix, and turning the DEFAULT
track flag option to NO for all subtitles streams.
MKVToolnix is available from http://www.bunkus.org/videotools/mkvtoolnix/

vlclua.c:  get rid of an empty module and fix descriptions

If someone wants to have it in there, it should probably rather be done
using a dedicated shortcut rather than a boolean configuration.

ptrdiff_t is signed so unequality comparison between pointers would
compute wrong when the two operands are within opposite halves of the
memory space.