Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

mdoc: add missing -width argument to Bl -tag.

mdoc: order prologue macros consistently by Dd/Dt/Os

Although groff_mdoc(7) gives another impression, this is the ordering
most widely used and also required by mdocml/mandoc.

Reviewed by: ru
Approved by: philip, ed (mentors)

Correct the HISTORY section of these man pages to show when the function,
not the "manual page example" was introduced.

Approved by: ed (mentor, implicit)
MFC after: 1 week

Remove an extra (commented out) .Sh HISTORY section heading, to avoid
the risk of "shadowing" the following .El request, and delete an empty
line to fix mdoc warnings.

MFC after: 3 days

Move the Internet Society copyright message so that it appears in the
formatted page as well as the source.

Add a new extensible GSS-API layer which can support GSS-API plugins,
similar the the Solaris implementation. Repackage the krb5 GSS mechanism
as a plugin library for the new implementation. This also includes a
comprehensive set of manpages for the GSS-API functions with text mostly
taken from the RFC.

Reviewed by: Love Hörnquist Åstrand <lha@it.su.se>, ru (build system), des (openssh parts)