Complete overhaul of the codec handling code:
*) obsolete flags `asymmetric codecs`, `symmetric codecs`, `reorder
codecs`
*) support proper codec offer/answer
*) split codec manipulation (strip/offer/accept/etc) into separate
functions for clarity and better code maintenance
*) fully update codec handlers in both directions after an answer
*) explicit allocation and handling of codecs and payload types in a
codec_store object
*) improve codec matchup logic during answer
*) more explicit handling of supplemental codecs (CN/DTMF)
*) remove now obsolete hacks for handling certain use cases
Change-Id: I996705ba8fe339524c2f70e6bb0fd854f9a1f4fb
Introduce generic "objects" with reference counting primitives and automatic
resource deallocation when no refs are left ("garbage collection"). Overhaul
poller framework to make extensive use of these objects to allow for future
thread-concurrent operation.
No locking added anywhere yet except in poller. Poller is still not 100%
thread safe, but close.
Valgrind reports no errors or memleaks.