Add `unit' member.
* fhandler_mem.cc (fhandler_dev_mem): Initialize `unit' as well.
(init): Care for differences between /dev/mem, /dev/kmem (not
implemented yet) and /dev/port.
(open): Change debug message to reflect the device.
(mmap): New function.
(munmap): Ditto.
(msync): Ditto.
(fstat): Use unit when setting st_dev in stat structure.
* mmap.cc (mmap): Handle MAP_ANONYMOUS flag.
Change error handling slightly.
* path.cc (get_device_number): Handle /dev/port.
4ea34a6850