Content Comparison

IN:
	  A = options
        A7 = even bank needed (for segment 0 allocation)
        A6 = fixed memory requested (no subject to swapping)
        A5 = from any slot
		A4 = any offset (generated and returned by call)
        A0-A1 = slot number if A5=0

      H = page offset ($00-$3F; $00 if A4 option set)
      L = number of pages wanted (1 to 64)

OUT:  Fc = 0
if empty         L = 0, always 
         Available memory found at bankpointer BH0BHL
      Fc = 1, A = RC_Room if not enough space in slot(s)

Registers changed after return:
     ....DEH./IXIY same
     AFBC...L/.... different