M4 fails to build against glibc 2.16.x, the shipped stdio.in.h attempts to
wrap gets() with a warning which fails since gets() got removed from the
default _GNU_SOURCE featureset.
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@32648 3c298f89-4303-0410-b956-a3cf2f4a3e73
