wide-dhcpv6: Compile for for uClibc-0.9.31.
We need -D_GNU_SOURCE. However, that also introduces a "dprintf" prototype, which clashes with our local dprintf. We use an ugly workaround. (Don't want to touch every caller of dprintf, because the patch would be huge.)


git-svn-id: svn://svn.openwrt.org/openwrt/packages@23802 3c298f89-4303-0410-b956-a3cf2f4a3e73