Moves more stuff from windows.h.
- include/winuser.h - interface relevant to user32.spec
- include/wine/winuser16.h - the old 16 bit interface (internal use)
- include/winbase.h - some minor updates to keep things coherent.
- Lot of other files made to include wine/winuser16.h, which is no
  longer included from windows.h

diff --git a/windows/class.c b/windows/class.c
index 416e4ee..ddd8efe 100644
--- a/windows/class.c
+++ b/windows/class.c
@@ -23,6 +23,7 @@
 #include "winproc.h"
 #include "debug.h"
 #include "winerror.h"
+#include "wine/winuser16.h"
 
 
 static CLASS *firstClass = NULL;