Function:     Bxx()
Purpose :     Draw a box on the screen with attribute and optional shadow
Usage   :     Bxx(<expN1>, <expN2>, <expN3>, <expN4>, <expN5>, [expN6] )
Params  :     expN1 - top row
              expN2 - left col
              expN3 - bottom row
              expN4 - right column
              expN5 - attribute to box
              expN6 - numeric shadow type  (default 0 - no shadow)
                      follow numeric keypad     |  7 8 9
                                                |  4 5 6
                                                |  1 2 3
              expN7 - shadow attribute (default 7 - grey on black)
              expC  - frame string - MUST be 9 characters - default single

Returns :     nothing.
Found in:     bxx.c