$FUNCNAME$
  MLEFTDOWN()
$CATEGORY$
  KEYBOARD/MOUSE
$SUMMARY$
   Determine the press status of the left mouse button
$SYNTAX$
     MLEFTDOWN() --> lIsPressed
$RETURNS$
     MLEFTDOWN() returns true (.T.) if the left mouse button is currently
     pressed; otherwise, it returns false (.F.).
$SEEALSO$
  MRIGHTDOWN()
$END$
