Misc (re #1751): added experimental option to enable/use worker thread for Python. To enable worker thread:
 - uncomment USE_THREADS in pjsip-apps/src/swig/python/Makefile
 - change USE_THREADS to True in pjsip-apps/src/pygui/application.py


git-svn-id: http://svn.pjsip.org/repos/pjproject@4798 74dad513-b988-da41-8d7b-12977e46ad98
Re #1751 Removed reference to libmilenage in ipjsua iOS

git-svn-id: http://svn.pjsip.org/repos/pjproject@4799 74dad513-b988-da41-8d7b-12977e46ad98
Re #1751: Fix build error when using 'disable-libsamplerate' on configure.



git-svn-id: http://svn.pjsip.org/repos/pjproject@4800 74dad513-b988-da41-8d7b-12977e46ad98
Re #1750 fix for detecting definition of CodecID in newer ffmpeg

git-svn-id: http://svn.pjsip.org/repos/pjproject@4801 74dad513-b988-da41-8d7b-12977e46ad98