tests/audio added: runs a series of state-machine based audio tests. (#195)

I didn't use the unit test framework for two reasons - one, I can't get it to work due to some lua include/require dir problems (could be windows-specific issue), and two, most of the "unit test framework" of luaunit is not useful for the purpose of testing the problems that usually need testing in multimedia applications.

I set this up as a SUCCESS/FAILURE thing at the moment for example, but often these things are better built as a fuzzy "just report # of voices and dump voice info" procedure, which is checked against log output that is verified as what we expect. And then, if a new log != expected log output, generate some error report for devs to look at. (and, by chance, many such "failures" are harmless or intentional, and verify new log as expected results and move on, etc).
16 jobs for master in 5 minutes and 3 seconds (queued for 7 seconds)
Status Name Job ID Coverage
  Build Shared
passed android-arm64-v8a #278378

00:00:15

passed android-armeabi-v7a #278377

00:00:14

passed android-x86 #278380

00:00:14

passed android-x86_64 #278379

00:00:15

passed libretro-build-ios-arm64 #278381
macosx-packaging

00:00:24

passed libretro-build-ios9 #278382
macosx

00:00:45

passed libretro-build-linux-i686 #278374

00:00:14

passed libretro-build-linux-x64 #278373

00:00:14

passed libretro-build-osx-arm64 #278375
macosx

00:00:16

passed libretro-build-osx-x64 #278376
macosx

00:00:19

passed libretro-build-tvos-arm64 #278383
macosx-packaging

00:00:18

passed libretro-build-windows-i686 #278372

00:00:15

passed libretro-build-windows-x64 #278371

00:00:26

 
  Build Static
passed libretro-build-ngc #278384

00:00:45

passed libretro-build-vita #278386

00:01:01

passed libretro-build-wii #278385

00:00:24