INT 21 - Phar Lap 386/DOS-Extender VMM - LIMIT PROGRAM'S CONVENTIONAL MEM USAGE
        AX = 2525h
        EBX = limit in 4k pages of physical conventional memory which program
              may use
Return: CF clear if successful
            EBX = maximum limit in pages
            ECX = minimum limit in pages
        CF set on error
            EAX = error code
                08h insufficient memory or -nopage switch used