Adds a child window(control) of ctype named name
with caption at ( x , y ) whose width and height is
( w , h ).
ctype is not an instance of the control-class but the class of
the child window.
style is additional styles for the childwindow such as WMsg::WS_BORDER.
You can set nil or "" for name. "" is for nameless control,
and nil is for the control which is nothing to do with vruby's control
management.