This also lists the objects from those two libraries as internal (by adding
the ff_ prefix) so that they can then be hidden via linker scripts.
(cherry picked from commit c6610a216e)
This makes the URL handling consistent - the URL hostname is used as
destination for the RTP packets, so the URL port should also belong to that.
Now the options announce_addr= and announce_port specify where the
announcements are sent.
Originally committed as revision 25424 to svn://svn.ffmpeg.org/ffmpeg/trunk
