A simple multi-thread stress test for PCM is added to test
subdirectory. It can perform various PCM update function in the
worker threads while reading/writing the data in the main thread.
It can help catching the unexpected error or blockage. For example,
running the capture test with a softvol plugin will lead to the assert
due to the races.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
