Moved most builtin controls structures into their respective C file.
Created new controls.h file private to user32.dll and moved remaining
builtin controls definitions there.

diff --git a/windows/message.c b/windows/message.c
index 49c0eed..ee656a0 100644
--- a/windows/message.c
+++ b/windows/message.c
@@ -26,7 +26,7 @@
 #include "selectors.h"
 #include "thread.h"
 #include "options.h"
-#include "menu.h"
+#include "controls.h"
 #include "struct32.h"
 #include "debugtools.h"