[glib] Add back required _XOPEN_SOURCE define

[Matthias Clasen <matthiasc src gnome org>]

commit 6dde6b7f21af0d3748f142c3f718f1d4cb21739e
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Nov 22 19:12:48 2011 -0500

    Add back required _XOPEN_SOURCE define
    
    This got lost somewhere between 2.30 and now, but it is needed
    for isnan(). See bug 664354, reported by Tim Mooney.

 glib/tests/strfuncs.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/glib/tests/strfuncs.c b/glib/tests/strfuncs.c
index 1dd2fca..d9e57d0 100644
--- a/glib/tests/strfuncs.c
+++ b/glib/tests/strfuncs.c
@@ -21,6 +21,7 @@
 
 #define GLIB_DISABLE_DEPRECATION_WARNINGS
 
+#define _XOPEN_SOURCE 600
 #include <ctype.h>
 #include <errno.h>
 #include <locale.h>