No functionnal change

It was useless for all other vout modules.

NullSoft format, what did I expect?

This converts meta-data properly.
This also fixes double conversion of the file path prefix (bug reported
on vlc mailing list).

Remove chunk merged upstream

This is bad, because many times you customize your vout configuration to make it work.

cf http://forum.videolan.org/viewtopic.php?f=14&t=65816&start=0

It fixes the last cross accessed variables.

 It allows to be sure to avoid infinite ping-pong between
VOUT_DISPLAY_CHANGE_DISPLAY_SIZE and VOUT_DISPLAY_EVENT_DISPLAY_SIZE in
some corner cases or broken "vout window".

fix a deadlock where the thread would be cancelled while still holding
message bank lock