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: m4-1.4.17/lib/stdio.in.h
===================================================================
--- m4-1.4.17.orig/lib/stdio.in.h	2013-10-16 14:41:01.678496227 +0300
+++ m4-1.4.17/lib/stdio.in.h	2013-10-16 14:41:48.849427839 +0300
@@ -717,10 +717,12 @@
 /* It is very rare that the developer ever has full control of stdin,
    so any use of gets warrants an unconditional warning; besides, C11
    removed it.  */
+#if defined gets
 #undef gets
 #if HAVE_RAW_DECL_GETS
 _GL_WARN_ON_USE (gets, "gets is a security hole - use fgets instead");
 #endif
+#endif
 
 
 #if @GNULIB_OBSTACK_PRINTF@ || @GNULIB_OBSTACK_PRINTF_POSIX@
