New file, containing GPL'ed code migrated out of

New file, containing GPL'ed code migrated out of
fts.c, with the following changes:
(setup_dir, free_dir): New functions.
(enter_dir): Now returns bool.  Return true if successful, false
if memory exhausted.  All callers changed.
Do not bother partly cleaning up on
memory allocation failure; that is free_dir's job.
However, free ad if hash_insert fails, to avoid memory leak.
(enter_dir, leave_dir): Accommodate change to FTS by inspecting
fts->fts_options to see which union member to use.