Subsdec: Split the decoder for subsdec / SSA / USF in three files, since the code has grown a bit too much in order to improve readability.
Some functions may still need to be renamed and moved from a file to another.
I hope it is done in the correct way, if not, tell me or revert.

control/media_instance.c: Support libvlc_MediaInstanceReachedEnd event for upcoming media_list_player.

Patch by Ilkka Ollakka

Yes, some sites use empty usernames

Patch by Hannes Domani
THANKS updated.

Closes #1249

Patch by Alexander Gall. Thanks.

This needs to be *reviewed*.

spotted by David Thiel

(bug reported by David Thiel)