INT 31 - CauseWay v1.3 - "SetMCBSize" - SET MCB MEMORY ALLOCATION BLOCK SIZE

	AX = FF28h
	ECX = new threshold (0000000h to disable MCB memory allocation system)
Return: CF clear if successful
	    threshold unchanged (default 16K)
	CF set on error (threshold > 64K)
Desc:	specify the memory allocation size below which CauseWay will use
	  internal MCB chains rather than allocating full 4K pages via DPMI
Note:	the specified threshold will be rounded up to the next higher multiple
	  of 4K
SeeAlso: AX=FF00h,AX=FF27h