Hide demuxers', muxers' and protocols' objects via the ld version script.
This reduces the symbols exported by libavformat from 699 to 451.
Signed-off-by: Mans Rullgard <firstname.lastname@example.org>
Add symbol versioning for shared libraries
Based on patch by Reinhard Tartler <siretart tauware de>
Originally committed as revision 21236 to svn://svn.ffmpeg.org/ffmpeg/trunk