ISO C11 removes the specification of gets() from the C language, eglibc 2.16+ removed it

Signed-off-by: Khem Raj <raj.khem@gmail.com>

Backported to guile 2.0.3 by Scott Garman <scott.a.garman@intel.com>

Upstream-Status: Pending

diff -urN guile-2.0.3.orig/lib/stdio.in.h guile-2.0.3/lib/stdio.in.h
--- guile-2.0.3.orig/lib/stdio.in.h	2011-10-22 07:19:35.000000000 -0700
+++ guile-2.0.3/lib/stdio.in.h	2012-12-12 20:47:06.397265942 -0800
@@ -711,11 +711,13 @@
 _GL_CXXALIAS_SYS (gets, char *, (char *s));
 #  undef gets
 # endif
+# if defined gets
 _GL_CXXALIASWARN (gets);
 /* 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.  */
 _GL_WARN_ON_USE (gets, "gets is a security hole - use fgets instead");
+# endif
 #endif