Int 21 Fn 2536  P - Phar Lap 386/dos-ext Vmm V3.0+ - Min/max Extended/con  [E]

   AX = 2536h
   EBX = bit flags
       bit 0: modifying conventional memory rather than extended memory
       bit 1: setting maximum memory usage rather than minimum
   ECX = new limit in 4K pages

Return: CF clear if successful
       EAX = new limit
   CF set on error
       EAX = error code (08h memory error or -NOPAGE set)
       EBX = maximum limit in pages
       ECX = minimum limit in pages