Add a note about return values of snd_pcm_state()

alsa-project/alsa-lib pull request #162 was opened from HEnquist:

This is a suggested improvement to the documentation of `snd_pcm_state()`. There is some confusion, probably caused by old bugs that could made it return a negative error code. This stuff is still floating around the internet and sometimes shows up in searches. This PR adds a comment intended to make it absolutely clear that there is never supposed to be a negative error code.

Request URL : https://github.com/alsa-project/alsa-lib/pull/162 Patch URL : https://github.com/alsa-project/alsa-lib/pull/162.patch Repository URL: https://github.com/alsa-project/alsa-lib