utils/alsa.m4: update for newer autoconf.

alsa-project/alsa-lib pull request #106 was opened from sezero:

fixes autoconf-2.70 warnings. should be compatible down to autoconf-2.59.

Request URL : https://github.com/alsa-project/alsa-lib/pull/106 Patch URL : https://github.com/alsa-project/alsa-lib/pull/106.patch Repository URL: https://github.com/alsa-project/alsa-lib