INT 21 u - LAN Manager Enhanced DOS - DosMailslotInfo                           
	AX = 5F4Fh
	BX = handle
Return: CF clear if successful
	    AX = max message size
	    BX = mailslot size
	    CX = next message size
	    DX = next message priority
	    SI = number of messages waiting
	CF set on error
	    AX = error code
SeeAlso: AX=5F4Dh,AX=5F4Eh,AX=5F50h