contrib: upnp: Work around missing WIN32 macro

When building in non-gnu -std, WIN32 doesn't get defined.

(cherry picked from commit fcafb389009c6913d58ebeadf54a4fcc9624652d)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

contrib/src/upnp/missing_win32.patch

+--- upnp_clean/upnp/inc/upnp.h	2015-04-30 14:37:26.962425889 +0200
++++ upnp/upnp/inc/upnp.h	2015-04-30 14:41:48.099528162 +0200
+@@ -41,6 +41,10 @@
+  * \file
+  */
+ 
++#ifdef _WIN32
++# define WIN32
++#endif
++
+ #include "ixml.h"
+ #include "upnpconfig.h"
+ #include "UpnpGlobal.h"

contrib/src/upnp/rules.mak

@@ -25,6 +25,7 @@ ifdef HAVE_WIN32
 endif
 	$(APPLY) $(SRC)/upnp/libupnp-ipv6.patch
 	$(APPLY) $(SRC)/upnp/miniserver.patch
+	$(APPLY) $(SRC)/upnp/missing_win32.patch
 	$(UPDATE_AUTOCONFIG) && cd $(UNPACK_DIR) && mv config.guess config.sub build-aux/
 	$(MOVE)