* Improve robustness of sample apps. Fixing crash in aviplay
* Changes in documentation
* Add first pjsua2 hello world sample (from PJSUA2 guide)
* Fix doxygen documentation for docs.pjsip.org v2
* Add make clean-doc target
* Replace Trac ticket URL with GitHub issues URL
* Remove pjsip-book because the correct one is in pjproject_docs
- Added a new API pjmedia_codec_passthrough_init2().
- Updated the initialization steps of passthrough codec in pjsua_media.c, to configure the codecs (of passthrough codec) to be enabled based on audio device extended/encoded formats.
- Minor update: added passthrough.h into pjmedia_codec.vcproj.
git-svn-id: https://svn.pjsip.org/repos/pjproject/trunk@2825 74dad513-b988-da41-8d7b-12977e46ad98