WEdit shouldn't draw frame over buttonbar.
When dragging a framed WEdit with the mouse, the frame is painted over the
buttonbar. This happens in two cases: when pressing the mouse down, and when
releasing it.
The patch fixes the problem by calling edit_update_screen() in these two cases.
This paints the buttonbar over the frame.
(The problem doesn't occur when moving the frame with the keyboard because
edit_callback(msg==MSG_KEY) calls edit_update_screen() right after handling the
key.)
Signed-off-by: Mooffie <mooffie@gmail.com>