vimeo playback now hides user agent automatically
Vimeo injects garbage into pages fetched by any user agent recognisable as
being VLC. Amended parse routine to check the current user agent; if the user
agent is set to VLC then parse returns a replacement playlist entry with the
same url but with an option setting the user agent to something that vimeo will
not trash.
The main playlist parsing loop then re-opens the stream with the correct agent
and calls vimeo.lua a second time; the stream is then parsed as before to get
the actual shortlived video url.
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>