Re #1776: Initial implementation of Libyuv wrapper. Supports:
 - library detection via autoconf
 - scaling and conversion function (from/to I420 or BGRA)



git-svn-id: http://svn.pjsip.org/repos/pjproject@4875 74dad513-b988-da41-8d7b-12977e46ad98
Misc (re #1751): Fixed possible bad assertion caused by race condition between regc_tsx_callback() and pjsip_regc_send() (thanks John Ryan for the report).



git-svn-id: http://svn.pjsip.org/repos/pjproject@4876 74dad513-b988-da41-8d7b-12977e46ad98
Misc (re #1751): Delete config.log and config.status on "make distclean/realclean".



git-svn-id: http://svn.pjsip.org/repos/pjproject@4877 74dad513-b988-da41-8d7b-12977e46ad98
Misc (re #1751): Updated configure script to pass params using "$@" (thanks Alexander Traud for the feedback).



git-svn-id: http://svn.pjsip.org/repos/pjproject@4878 74dad513-b988-da41-8d7b-12977e46ad98
Fix #1777: Problem in audio device list refresh after unregistering an audio device factory.



git-svn-id: http://svn.pjsip.org/repos/pjproject@4879 74dad513-b988-da41-8d7b-12977e46ad98