Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

pathchk(1): Fix the example so it allows arbitrary pathnames.

Spaces and various other characters in pathnames are not passed through
literally by xargs in its default mode. Instead, use find . -exec ... {} +

Although the -- argument is not strictly required here, add it anyway to
avoid surprises when modifying the code to find -f -somedir ...

MFC after: 1 week

pathchk: Add the new POSIX -P option.

This option checks for empty pathnames and components starting with '-'.
Our -p option also checks for the latter, which remains the case.

MFC after: 1 week

Sort sections.

Added the EXIT STATUS section where appropriate.

Uniformly refer to a file system as "file system".

Approved by: re

mdoc(7) police: tidy up the markup.

Add the pathchk utility, which checks pathnames for validity or
portability between POSIX systems.

Submitted by: Chuck Rouillard (manpage, initial implementation)