[glib] config.h.win32.in: Define _WIN32_WINNT Conditionally

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

commit e3db9632e7e8a1e4177f503aa9ffa184a991e8a4
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Fri May 23 10:14:16 2014 +0800

    config.h.win32.in: Define _WIN32_WINNT Conditionally
    
    This is done so that _WIN32_WINNT may be overridden in the project files,
    if needed, so that one can access the Vista+ (or so) Windows APIs easier
    by using "preprocessor defines" (or so) in the Visual C++ project files.

 config.h.win32.in |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/config.h.win32.in b/config.h.win32.in
index d5cf8c0..aa700e3 100644
--- a/config.h.win32.in
+++ b/config.h.win32.in
@@ -208,7 +208,9 @@
 /* #undef HAVE_HASMNTOPT */
 
 /* Target the Windows XP API */
+#ifndef _WIN32_WINNT
 #define _WIN32_WINNT 0x0501
+#endif
 
 #if _WIN32_WINNT >= 0x0600
 /* if_indextoname() and if_nametoindex() are available on Windows Vista/Server