Improve mac-avcapture logging

Log messages are now prefixed with the source name to distinguish between
multiple sources
Refactor mac-avcapture cleanup and improve session init error handling
Move device handling in mac-avcapture to separate functions
Fix minor style-deviation in mac-avcapture
Improve preset selection robustness in mac-avcapture
Enable device selection for mac-avcapture
Add connect/disconnect handling for mac-avcapture
libobs:  Account for volume with audio levels
libobs:  Fix switch warning
UI: Remove unused variable
CoreAudio: Enumerate AudioDeviceID manually

Apparently, despite the fact that Apple added
kAudioHardwarePropertyTranslateUIDToDevice in 10.8, it's not actually
usable in 10.8, only 10.9.  So, instead of being able to use it like a
normal, sane person, we have to enumerate all devices manually and find
the AudioDeviceID ourselves.  A slight annoyance and a mark against
apple's competence, but audio devices should now be working again on
10.8 at least, so whatever.
OpenGL: Fix erroneous handling of BGRX

BGRX was being treated as "BGR input" with "RGBA storage", where it
should have been "BGRA input" with "RGB storage".  So the input for the
texture was expecting 24 bits of packed BGR rather than 32bit BGRX
pixels, and was internally storing it with alpha available.
ignore test-random alpha (to ensure BGRX works)
OpenGL:  Don't name VS inputs as 'geom' inputs.

Geometry shaders come after vertex shaders, not before.
OpenGL: Don't call glGetAttribLocation on outputs

Previously we were using glGetAttribLocation on all inputs/outputs and
then just discarding if it was returned -1.  However, we have a boolean
value of 'input' in gl_parser_attrib, so there's no need to be doing
this and discarding potentially useful error handling information.
Slight modification of mixing function
Merge pull request #112 from antihax/Opt

Slight modification of audio mixing function
Remove property list prefill code in mac-avcapture
Change graphics subsystem to 4x4 matrices

4x4 matrices aren't as optimal, but are much more sensible to handle
when you want to do more advanced stuff like scaling, skewing, or
inversion.
Merge pull request #113 from jp9000/matrix-update

Change graphics subsystem to 4x4 matrices