eglibc has remove gets starting 2.16
therefore check for its being there before 
undefining it.

Upstream-Status: Pending
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Index: m4-1.4.16/lib/stdio.in.h
===================================================================
--- m4-1.4.16.orig/lib/stdio.in.h	2011-03-01 08:39:29.000000000 -0800
+++ m4-1.4.16/lib/stdio.in.h	2012-07-03 08:32:08.145935928 -0700
@@ -161,8 +161,10 @@
 /* It is very rare that the developer ever has full control of stdin,
    so any use of gets warrants an unconditional warning.  Assume it is
    always declared, since it is required by C89.  */
+#if defined gets
 #undef gets
 _GL_WARN_ON_USE (gets, "gets is a security hole - use fgets instead");
+#endif
 
 #if @GNULIB_FOPEN@
 # if @REPLACE_FOPEN@