Improvements to the Win32 screen driver

Improvements to the Win32 screen driver

 . Rationalized names and the interface to some primitives.

 . Added screen name feature (like X version)

 . Ensured that windows are closed before exit / disk-restore.

 . Fixed bug in screen resize (you *have* to guard against resizing to
   the same size otherwise the rest of the system allocates new
   matrixes and then decides to optimize the screen reorganization,
   leading to random stuff being copied from the uninitialized
   matrixes to the screen).

 . The Close Window menu item now closes the window if there are more
   than one, otherwise it behaves like ^X ^C

 . Debugged multiple screens.  Added a whole load of black magick for
   keeping Edwin's idea of the selected-screen in synch with the
   Windows screen with the input focus.

 . There is no need to hide the cursor (Caret) during redisplay as
   windows does this anyway, and manually hiding it causes visible
   caret flicker.