MSC: unsigned _dos_setblock( unsigned size, unsigned seg,
					unsigned *maxsize )


	- prototype in dos.h

	- size = new block size
	- seg = segment of DOS memory block to change
	- maxsize = size of buffer actually allocated if size not available

	- returns 0 on success or DOS error code on failure

	- Turbo C uses setblock()
	- see	INT 21,4A   _dos_allocmem()   _dos_freemem()