Partial merge with recent revisions[1] from FreeBSD.

Partial merge with recent revisions[1] from FreeBSD.

Highlights:
- Use a larger field for the size in blocks; the current width
  (4 digits) is only good for 5 MB.
- Introduce a new primary `-depth n', which tests whether
  the depth of the current file relative to the starting
  point of the traversal is n. The usual +/- modifiers
  to the argument apply.
- Support SysV-style -exec args {} + function, required by SUSv3.
- Remove partial support for building on NetBSD.
- Lots of style(9) work.
- Update manual page.

Features not merged:
- The -acl option for locating files with extended ACLs.

Submitted-by: Alexander 'alxl' Lobachov <alxl_at_alxl_dot_info>
[1] Makefile:1.17 extern.h:1.22 find.1:1.71 find.c:1.17 find.h:1.17
    function.c:1.52 getdate.y:1.3 ls.c:1.17 main.c:1.15 misc.c:1.7
    operator.c:1.14 option.c:1.23