[gupnp] Prevent redefinition of _WIN32_WINNT

[Jens Georg <jensgeorg src gnome org>]

commit c7b9dd58fa3d382704cac23f08975469947bfb29
Author: Jens Georg <mail jensge org>
Date:   Fri Feb 8 18:51:21 2013 +0100

    Prevent redefinition of _WIN32_WINNT

 libgupnp/gupnp-windows-context-manager.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/libgupnp/gupnp-windows-context-manager.c b/libgupnp/gupnp-windows-context-manager.c
index c888507..662c009 100644
--- a/libgupnp/gupnp-windows-context-manager.c
+++ b/libgupnp/gupnp-windows-context-manager.c
@@ -30,7 +30,9 @@
 
 #include <config.h>
 #include <string.h>
+#ifndef _WIN32_WINNT
 #define _WIN32_WINNT 0x0502
+#endif
 #include <winsock2.h>
 #include <ws2tcpip.h>
 #include <iphlpapi.h>