* configure.ac (_FORTIFY_SOURCE): Do not multiply define.

This ports to Gentoo.  Problem originally reported against coreutils,
but Emacs has it too.

Fixes: debbugs:12714

ChangeLog

+2012-10-23  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* configure.ac (_FORTIFY_SOURCE): Do not multiply define (Bug#12714).
+	This ports to Gentoo.  Problem originally reported against coreutils,
+	but Emacs has it too.
+
 2012-10-23  Glenn Morris  <rgm@gnu.org>
 
 	* Makefile.in (emacs_transform): Remove.

configure.ac

@@ -743,7 +743,7 @@ else
   AH_VERBATIM([FORTIFY_SOURCE],
   [/* Enable compile-time and run-time bounds-checking, and some warnings,
       without upsetting glibc 2.15+. */
-   #if defined __OPTIMIZE__ && __OPTIMIZE__
+   #if !defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__
    # define _FORTIFY_SOURCE 2
    #endif
   ])