Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

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

Approved by: re

o Reflect repo-copy of extattr.[c3] from libutil to libc, moving
extattr namespace routines to the libc/posix1e directory. While
the extattr calls are not strictly POSIX.1e, POSIX.1e wasn't
strictly ever approved, so I think that's OK.

Obtained from: TrustedBSD Project

mdoc(7) police: Use the new .In macro for #include statements.

Add RETURN VALUES and ERRORS sections.

Add a manual page for extattr_string_to_namespace and
extattr_namespace_to_string.

Reviewed by: rwatson