[package/coreutils] fix errors in shipped stdio.in.h

gets() got dropped in eglibc version 2.16 - so no need to wrap it

Signed-off-by: Mirko Vogt <mirko@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/packages@37327 3c298f89-4303-0410-b956-a3cf2f4a3e73