[USER32] Fix OEM resources compilation due to missing OBM_, OIC_, OCR_ defines...

... addendum to commits 072965eb0 and 6cdaad13b.

Due to the wrapping of these defines within an #ifdef OEMRESOURCE block
in winuser.h (for MS PSDK compatibility), these defines became unavailable
in user32.rc resource file. Thus, during user32 resources compilation,
the resource compiler fell back to the behaviour of considering these
resource IDs as literal string IDs (not numerical ones).

Thus, whenever code was trying to refer to these resources via their
numerical IDs, these resources could not be found now, rendering ReactOS
unusuable.

win32ss/user/user32/user32.rc

@@ -1,4 +1,5 @@
 #include <windef.h>
+#define OEMRESOURCE
 #include <winuser.h>
 
 #include "include/resource.h"