empty functions for audio output thread creation.
Merge branch 'master' into audio_output

Conflicts:
	include/libaudioverse/private_threads.h
add audio_output.c to build
Functions to create and join with/free threads
Audio_output: can initialize a thread that does nothing

This involved minor thread refactoring and cleanup.
Logic to init portaudio.
Added a member to graphs to store thread handle
Logic to make portaudio stream

This is not in the thread, but the function that makes it:
putting it in the thread means we can't indicate failure.
Revert "Logic to make portaudio stream"

This reverts commit e3f360089bcdb6d2787bc7edf1a9d3567bb1cc8d.
Began implementation of a threadsafe ringbuffer

Writing does not work as of this commit, and code does not compile.
Flagged a bunch of stuff with Lav_PUBLIC_FUNCTION
Fixed compile errors.

Ringbuffer still doesn't compile; it isn't in CMakeLists.txt.
Actually properly moved threads.cpp
Finished and refactored preliminary threadsafe ringbuffer
Fixed the tests.
Renamed crossThreadRingBuffer functions to use CBRT prefix and updated header
Began test for CTRB and fixed create function
Finished the ringbuffer test
actually update the CTRB write position
Fixed CTRBGetAvailableReads