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)

mdoc(7) police: "The .Fn function".

This API will appear in FreeBSD 4.6.

Introduce a version field to `struct xucred' in place of one of the
spares (the size of the field was changed from u_short to u_int to
reflect what it really ends up being). Accordingly, change users of
xucred to set and check this field as appropriate. In the kernel,
this is being done inside the new cru2x() routine which takes a
`struct ucred' and fills out a `struct xucred' according to the
former. This also has the pleasant sideaffect of removing some
duplicate code.

Reviewed by: rwatson

Fix typos getpeerid -> getpeereid.

PR: docs/32442
Reviewed by: dd

Use .In, .Ux, and .Rv where appropriate. Also consistently call this
a "function" instead of a "routine".

Submitted by: ru

Implement getpeereid(3), a front-end to the LOCAL_PEERCRED
socket option for the Unix domain. It's weaker than the
socket option (this only returns the uid and gid, while the
socket opt. can return the entire group list), and is
implemented mostly for compatibility with OpenBSD.