[Enhancement] aplay: make stream pause/resume automation/script friendly

[GitHub issues - opened]

alsa-project/alsa-utils issue #155 was opened from aiChaoSONG:

There is an `-i` option for interactive mode, in the interactive mode, we are able to pause/resume the playback/capture stream with SPACE key, which is very good. However we have to do this in a terminal, because there is a isatty check on the stdin, this is not friendly for automation/script to test audio pause/resume feature with aplay.

Is it possible to remove the isatty check, so that we can do pause/result test with a single stdin redirection? Another possible fix is that we can make use of the SIGUSR2, so that we pause/resume stream by sending signal to the aplay process.

@perexg

Issue URL     : https://github.com/alsa-project/alsa-utils/issues/155
Repository URL: https://github.com/alsa-project/alsa-utils