On SoundSDL destructor and `reset()`, there was a deadlock with Linux
pthreads, it happened sometimes that the reader thread would call
`SDL_SemWait(data_available)` while `deinit()` would destroy the
semaphore and the `SDL_SemWait()` would end up waiting forever on a null
semaphore.

Change the sequencing of deinit() to prevent this from happening, set
`initialized = false` at the beginning of the sequence to prevent
subsequent entries into the reader callback, and add an SDL_Delay(100)
between the final `SDL_SemPost()` and `SDL_UnlockMutex()`s and the
`SDL_DestroySemaphore()` and `SDL_DestroyMutex()`s to allow a running
reader to complete with a valid mutex and semaphores before they are
destroyed and the thread is joined.

Resetting the sound system also sometimes triggers a memory corruption
bug, but that's a separate issue.