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>

share/lua/playlist/vimeo.lua

@@ -42,6 +42,13 @@ end
 
 -- Parse function.
 function parse()
+    agent = vlc.var.inherit(nil,"http-user-agent")
+
+    if string.match( string.lower(agent), ".*vlc.*" ) then
+        vlc.msg.dbg("Wrong agent, adapting...")
+        return { { path = vlc.access .. "://" .. vlc.path; options = {":http-user-agent=Mozilla/5.0" } } }
+    end
+
     _,_,id = string.find( vlc.path, "vimeo.com/([0-9]*)")
     prefres = get_prefres()
     ishd = false