int pascal RectTile(RECT a, RECT b, RECT r[])

  This function takes two rectangles, a and b,  and returns five
rectangles which represents the tiling of a and b. The tiling
operation is illustrated below :

        +-----------------------+     +-----------------------+
        |a                      |     |r0    |r1    |r4       |
        |      +------+         |     |      |------|         |
        |      |b     |         |  -->|      |r2    |         |
        |      +------+         |     |      |------|         |
        |                       |     |      |r3    |         |
        +-----------------------+     +-----------------------+

  This function is useful if you want to generate update rectangles for
a redrawing operation.

Parameters
  a and b are two RECT structures.
  r must be defined in the calling routine as RECT r[5]. This will
   contain the five rectangles which result from the tiling operation.

Returns
  Nothing.