Int 21 Fn 251B  P - Phar Lap 386/dos-extender Vmm - Unlock Pages           [E]

   AX = 251Bh
   EDX = number of pages to unlock
   if BL = 00h
       ECX = linear address of first page to unlock
   if BL = 01h
       ES:ECX -> pointer to first page to unlock

Return: CF clear if successful
   CF set on error
       EAX = error code
       09h invalid address range

See Also: AX=251Ah,AX=EB07h,INT 31/AX=0601h