FUNCTION RAT_ISMOUSE()

  Short:
  ------
  RAT_ISMOUSE() Determines mouse usage by RAT_EVENT()

  Returns:
  --------
  <lIsMouse> => is there a mouse

  Syntax:
  -------
  RAT_ISMOUSE([lIsMouse])

  Description:
  ------------
  Determines mouse usage by RAT_EVENT(). Default is
  determined by a call to the ASM function RAT_EXIST(). However,
  you may want to shut down mouse usage even if a mouse is
  present. If so, call this function with False, to override.

  [lIsMouse]  S_MOOSE.PRG contains a static variable
  called 'ismouse'. This is determined initially by a call to
  RAT_EXIST(), but may be overridden by calling RAT_ISMOUSE(.f.).

  Examples:
  ---------
   RAT_ISMOUSE(.f.).

  Source:
  -------
  S_MOOSE.PRG