* fhandler.h: Add device type FH_RANDOM. Add class
fhandler_dev_random.
* fhandler_random.cc: New file. Implementation of
fhandler_dev_random.
* hinfo.cc (build_fhandler): Add case for FH_RANDOM.
* path.cc: Add device names for random devices to
windows_device_names.
(get_device_number): Add if branch for random devices.
(win32_device_name): Add device name generation for
random devices.
winsup.h: Include <wincrypt.h>.