[glib] gmacros.h: offsetof is also available on MSVC

[Chun-wei Fan <fanchunwei src gnome org>]

commit 92e31896137c18434f599edcc5bb3729b2dd4e70
Author: Nirbheek Chauhan <nirbheek centricular com>
Date:   Mon Jul 11 18:17:34 2016 +0530

    gmacros.h: offsetof is also available on MSVC
    
    All versions since Visual C++ 2005 have this available, so we can just
    use it for G_STRUCT_OFFSET.
    
    See: https://msdn.microsoft.com/en-us/library/dz4y9b9a.aspx

 glib/gmacros.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/glib/gmacros.h b/glib/gmacros.h
index 9113221..7583479 100644
--- a/glib/gmacros.h
+++ b/glib/gmacros.h
@@ -311,7 +311,7 @@
  * fields through their offsets.
  */
 
-#if defined(__GNUC__)  && __GNUC__ >= 4
+#if (defined(__GNUC__)  && __GNUC__ >= 4) || defined (_MSC_VER)
 #define G_STRUCT_OFFSET(struct_type, member) \
       ((glong) offsetof (struct_type, member))
 #else