Cherry-pick vendor changes to mdoc:

: 2011-10-23 Ingo Schwarze <schwarze@openbsd.org>
:
: [mdoc] Synchronize string tables with the mandoc(1) utility.
:
: * tmac/doc-common: Add many architecture names used in NetBSD and
: OpenBSD (and "arm" from FreeBSD) and remove the duplicate OS version
: entry for Darwin-10.6.0.
:
: * tmac/doc-syms: Add many library names used in NetBSD and FreeBSD.
:
: * tmac/groff_mdoc.man: Document all supported architecture names, OS
: versions, and library names.
:
: 2011-09-11 Joseph Koshy <jkoshy@users.sourceforge.net>
:
: [mdoc] Add some library strings.
:
: * tmac/doc-syms: Add libdwarf' and libelf'.
: * tmac/groff_mdoc.man: Document them.
:
: 2011-07-03 Guillem Jover <guillem@debian.org>
:
: mdoc: Update more OS versions strings.
:
: * tmac/doc-common: Add versions strings for NetBSD, OpenBSD,
: FreeBSD, and DragonFly.