* path.cc (get_device_number): Remove special com? consideration.

* path.cc (get_device_number): Remove special com?  consideration.
(special_chars): Make static.
(special_introducers): New.
(special_char): Allow specified valid_chars args.
(fnunmunge): Handle aux-like filenames correctly.
(special_name): Add con, conin$, conout$.
(mount_item::fnmunge): Use __small_sprintf return value to calculate
increments.