Re #1758: Initial implementation of OpenH264 wrapper. Supports:
 - library detection via autoconf
 - CBP
 - packetization modes: 0, 1
 - key frame request and indication
 - obey remote's fmtp

Also added video codec test in samples (similar to the one in pjmedia test though).
And there are some fixes here and there too (e.g. in vid_codec_util.c).


git-svn-id: http://svn.pjsip.org/repos/pjproject@4815 74dad513-b988-da41-8d7b-12977e46ad98