Int 21 Fn 2507  P - Phar Lap 386/dos-extender - Set Real- & Protected-mod  [E]

   AX = 2507h
   CL = interrupt number
   DS:EDX = CS:EIP of protected-mode interrupt handler
   EBX = CS:IP of real-mode interrupt handler

Return: CF clear

Notes: interrupts are disabled until both vectors have been modified
   this function is also supported by FlashTek X-32VM

See Also: AX=2504h,AX=2505h