fts: Move private flags away from public ones.

[des]

Summary

Renumber the private flags so there is a sizeable gap between them and
the public flags, making it easier to add public flags in the future.
These private flags are only ever set or read by FTS itself, so there
is no compatibility issue.

MFC after: 1 week
Sponsored by: Klara, Inc.

[markj]

include/fts.h

49–64

I see a reference to FTS_NAMEONLY in ls.c, so this seems to be a de facto public flag and thus shouldn't be changed?

[des]

include/fts.h

49–64

Ah, you're right, it's a special case because it can't be passed to fts_open() but it gets set temporarily if passed to fts_children(). I'll have to revise the patch.

[des]

update

[markj]

This is probably ok. I couldn't find any examples of third-party code actually using this flag.