change getopt_long return variable from char to int

alsa-project/alsa-utils pull request #275 was opened from sadguitarius:

fixes #274

Request URL : https://github.com/alsa-project/alsa-utils/pull/275 Patch URL : https://github.com/alsa-project/alsa-utils/pull/275.patch Repository URL: https://github.com/alsa-project/alsa-utils