[glib] Fix broken build with -Wundefined

[Kjartan Maraas <kmaraas src gnome org>]

commit 3fe710c0b59b881c7b4090601f8c1a33876af78d
Author: Kjartan Maraas <kmaraas gnome org>
Date:   Tue Jan 17 17:10:19 2012 +0100

    Fix broken build with -Wundefined

 glib/gmacros.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/glib/gmacros.h b/glib/gmacros.h
index 4fc20bf..accd55a 100644
--- a/glib/gmacros.h
+++ b/glib/gmacros.h
@@ -343,7 +343,7 @@
 #define G_DEFINE_CONSTRUCTOR(_func) static void __attribute__((constructor)) _func (void);
 #define G_DEFINE_DESTRUCTOR(_func) static void __attribute__((destructor)) _func (void);
 
-#elif _MSC_VER >= 1500
+#elif defined (_MSC_VER) && (_MSC_VER >= 1500)
 /* Visual studio 2008 and later has _Pragma */
 
 #define G_HAS_CONSTRUCTORS 1