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/user.c b/windows/user.c
index 43f7f57..137d65f 100644
--- a/windows/user.c
+++ b/windows/user.c
@@ -16,7 +16,7 @@
 #include "queue.h"
 #include "win.h"
 #include "clipboard.h"
-#include "menu.h"
+#include "controls.h"
 #include "cursoricon.h"
 #include "hook.h"
 #include "toolhelp.h"