[gtk+] Allow building with CFLAGS=-Werror

[Javier JardÃn <jjardon src gnome org>]

commit 094fcd6fb7609361a864c6f3473791bf849c6bbc
Author: Stef Walter <stef memberwebs com>
Date:   Sat Aug 11 03:12:39 2012 +0900

    Allow building with CFLAGS=-Werror
    
    Allow building using:
    
    $ CFLAGS=-Werror sh autogen.sh --prefix=/xxx

 configure.ac |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 6fea3af..41e24a3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -987,11 +987,13 @@ if test "x$enable_x11_backend" = xyes; then
 
   AC_MSG_CHECKING([if <X11/extensions/XIproto.h> is needed for xReply])
   AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <X11/Xlibint.h>]],
-                                     [[xReply *rep;]])],
+                                     [[xReply *rep = NULL;
+                                       rep = rep;]])],
                     [AC_MSG_RESULT([no])],
                     [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <X11/extensions/XIproto.h>
                                                           #include <X11/Xlibint.h>]],
-                                                        [[xReply *rep;]])],
+                                                        [[xReply *rep = NULL;
+                                                          rep = rep;]])],
                                        [AC_MSG_RESULT([yes])
                                         AC_DEFINE([NEED_XIPROTO_H_FOR_XREPLY], [1],
                                                   [Define if <X11/extensions/XIproto.h> needed for xReply])],