Move gettail_dir more closely to its usage.
Add os_stat to os/fs module.
Refactor fullpathcmp -> path_full_compare.
Test and refactor gettail -> path_tail.
Test and refactor gettail_sep -> path_tail_with_seperator.
Test and refactor getnextcomp -> path_next_component.
Fix seperator->separator, path_tail_with_separator->path_tail_with_sep.
Initialize on declaration; use postincrements.
Rename FPC_* constants.