[gtk+] Avoid redefining GNU_SOURCE

[Matthias Clasen <matthiasc src gnome org>]

commit e171f4930bcea3ba8c2de8327e408d842dcbe12d
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Mar 23 15:13:33 2017 +0000

    Avoid redefining GNU_SOURCE
    
    Gives a compiler warning with the wrong flags.

 tests/gtkgears.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)
---
diff --git a/tests/gtkgears.c b/tests/gtkgears.c
index d46f598..32a24da 100644
--- a/tests/gtkgears.c
+++ b/tests/gtkgears.c
@@ -35,7 +35,6 @@
  * Jul 13, 2010
  */
 
-#define _GNU_SOURCE
 #include "config.h"
 
 #include <math.h>