ucm: use closefrom instead of close_range

ucm: use closefrom instead of close_range

closefrom is a library function with a fallback mechanism for when the
kernel does not support the close_range syscall.

Also check for the function properly instead of assuming it is available
with _GNU_SOURCE defined.

Closes: https://github.com/alsa-project/alsa-lib/pull/486
Fixes: https://github.com/alsa-project/alsa-lib/issues/485
Signed-off-by: Mike Gilbert <floppym@gentoo.org>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>