Screen change area data structure.

typedef struct _SCA {
  SCA       pscaNext;                                             /*  Linked list pointer. */
  ULONG     cRects;                                               /*  Number of rectangles in area. */
  RECTL     arcl[MAX_SCA_RECTS+1];         /*  Rectangle dimensions. */
  ULONG     aulRectSize[MAX_SCA_RECTS+1];  /*  Cached rectangle sizes. */
} SCA;

typedef   SCA   * PSCA ;