Update RageSoundDriver_AU.cpp

The Yosemite crash happens when we call CFRunLoopAddObserver. It doesn't seem to like runLoopRef. Replacing the first argument to this call with CFRunLoopGetCurrent() avoids the crash, but the app then hangs because CFRunLoopWakeUp doesn't cause observerRef (NameHALThread) to fire, so the semaphore is not posted. Commenting the semaphore wait line allows the game to boot in Yosemite, and seems to play totally normally. This doesn't really fix our problem (we are trying to name the HAL thread, and a catastrophic error occurs), but it shows us what the problem is.

We are obtaining runLoopRef using an API call that was deprecated years ago. However, the Apple-approved replacement code doesn't produce a runLoopRef that avoids the crash, either. So I'm not sure how we get the correct runLoopRef so we can name the thread.

This is my first time looking at the code base, but I don't see the value of naming the thread. In the interest of keeping Stepmania compatible with the upcoming operating system, I propose we just remove the thread-naming logic.