Added tmschema.h and some other theme defines.

include/winuser.h

diff --git a/include/winuser.h b/include/winuser.h
index eff497c..bc3d628 100644
--- a/include/winuser.h
+++ b/include/winuser.h
@@ -1110,6 +1110,8 @@
 #define WM_MOVING	    0x0216
 #define WM_POWERBROADCAST   0x0218
 #define WM_DEVICECHANGE     0x0219
+/* Win32 5.1 messages */
+#define WM_THEMECHANGED     0x031A
 
 /* wParam for WM_SIZING message */
 #define WMSZ_LEFT           1