audio/gmpc-plugins: Patched SlackBuild.
audio/gmpc-plugins: Patched SlackBuild.

Fixes failure to build with glibc-2.21 (-current).

Signed-off-by: David Spencer <baildon.research@googlemail.com>

Signed-off-by: Willy Sudiarto Raharjo <370971f3b2b804ed58e63f6bfe153fc3c112b006@slackbuilds.org>

panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds