Fixed a Win32 constant missing after upgrading to gcc 4.4 headers

git-svn-id: https://sfml.svn.sourceforge.net/svnroot/sfml/trunk@1407 4e206d99-4929-0410-ac5d-dfc041789085

src/SFML/Window/Win32/WindowImplWin32.cpp

@@ -36,13 +36,16 @@
 #include <iostream>
 #include <vector>
 
-// Old versions of MinGW lack the definition of XBUTTON1 and XBUTTON2
+// MinGW lacks the definition of some Win32 constants
 #ifndef XBUTTON1
     #define XBUTTON1 0x0001
 #endif
 #ifndef XBUTTON2
     #define XBUTTON2 0x0002
 #endif
+#ifndef MAPVK_VK_TO_VSC
+    #define MAPVK_VK_TO_VSC (0)
+#endif
 
 
 namespace sf