INT 67 - Virtual Control Program Interface - ALLOCATE A 4K PAGE
        AX = DE04h
Return: AH = 00h successful
            EDX = physical address of allocated page
        AH nonzero: failed
Notes:  the client program is responsible for freeing all memory allocated
          with this call before terminating
        also available in protected mode by calling the protected-mode VCPI
          entry point
SeeAlso: AX=DE03h,AX=DE05h