Added msg().

  This function draws a message on the screen.
  Added msg(), removed test_function().

  We can now draw a message on the screen from lua.
  Added more code.

  on_idle() now uses the new msg() primitive
  Now we have some graphics stuff coded.

  The screen init function has been moved ,and the on_idle
 function in lumail.lua will update the status-bar with the
 current date/time.

  Link in libncurses, now we use it