Int 21 Fn 252B  P - Phar Lap 386/dos-extender - Virtual Memory Management  [E]

   AX = 252Bh
   BH = function
       05h lock pages
       06h unlock pages
   BL = address type
       00h linear address
       ECX = linear start address of memory region
       01h segmented address
       ES:ECX -> start of memory region
   EDX = size of memory region in bytes

Return: CF clear if successful
   CF set on error

Note:  this function is also supported by FlashTek X-32VM; if X-32 is not
     using virtual memory, this function always succeeds