SaveScr()

         Saves a screen region

    Syntax:

         SaveScr( nY1, nX1, nY2, nX2, nEffect ) -> aPantalla

         nY1     : Upper left Y coordinate
         nX1     : Upper left X coordinate
         nY2     : Lower right Y coordinate
         nX2     : Lower right X coordinate
         nEffect : A numeric value indicating the type of effect
                   1 -> left - right
                   2 -> right - left
                   3 -> up - down
                   4 -> down - up

    Description:

         Saves a screen region that come be later restores with RestScr().

    Return:

         Saved screen region.

    Example:

         nMode := 1
         aScr  := SaveScr ( 10, 10, 20, 70, nMode )
         DispBox ( 10, 10, 20, 70, "+-+|+-+| ", "W/B"  )
         Inkey(1)
         RestScr ( 10, 10, 20, 70, aScr )