libvlc API: Add Marquee Filter to libvlc in video.c

libvlc API: Add Marquee Filter to libvlc in video.c

-libvlc_video_get_marquee_option_as_int    : get an option int value
-libvlc_video_get_marquee_option_as_string : get an option string value
-libvlc_video_set_marquee_option_as_int    : enable, disable or set an int value
-libvlc_video_set_marquee_option_as_string : set a string value to marq

Modified patch from Cyril Mathe <cmathe@actech-innovation.com>

This API implementation is very limitied, as no presistent state is preserved, and settings can only be set when a vout is around. This makes the whole thing very limitating.

Hopefuly we'll get a better implementation over the time.