Port testmultiaudio

Splitting this into two files since we can't have two event loops.
add testmultiaudio2 to the makefile
Merge pull request #12 from gsathya/testmultiaudio

port Testmultiaudio
remove joystick button mapping (handled by gamecontrollerdb)
Don't get display when creating window

There's nothing being done with the display currently.
Return an error if we don't find a compatible audio format
Refactor duplicate code in HandleAudioProcess