libpythagoras needs libm.

This fixes "make tinderbox" failures on various architectures when
WITH_TESTS=yes is enabled.  Problem introduced in r267679.
Allow console drivers active from early boot to be used with xf86-video-scfb,
rather than only drivers attached later on. This involves a small amount of
code duplication with dev/fb/fbd.c, which will fixed later on.

Also improve performance of vt_blank() by making it not read from the
framebuffer unnecessarily.
Allow efifb to be used with xf86-video-scfb. This is important for EFI
systems without either a CSM or real graphics drivers, such as my Lenovo
Haswell laptop.

This provides working X with the small complication of a console cursor
permanently overlaid on the upper-left corner of the screen that will be
dealt with later.

Also remove some redundant screen clearing.
Revert previous revision (r268461) for reasons documented in PR.
To use tmux in an rc.d script, use the new-session flag "-d".
To use screen in an rc.d script, use the "-dm" flag.
If you really need to launch an attached session, manually
export TERM=xterm (FreeBSD 9.0 or higher) or export TERM=cons25
for older releases.

Reported by:	bdrewery
Discussed on:	src-committers, svn-src-all, svn-src-head
PR:		bin/191869
After r261991, clang warnings about unused functions in the kernel were
completely silenced.  Make sure these warnings appear again, so there is
some incentive to fix them, but do not error out the whole kernel build
for them.

Noticed by:	steven@pyro.eu.org
PR:		191867
MFC after:	3 days
Implement pmap_unwire().  See r268327 for the motivation behind this change.
Add emulation for legacy x86 task switching mechanism.

FreeBSD/i386 uses task switching to handle double fault exceptions and this
change enables that to work.

Reported by:	glebius
Enable MK_TESTS by default, take 2.

This is a redo of r267424, which was reverted in r267432 because it broke
"make buildworld" from FreeBSD 9.x.  This issue has been resolved and this
change is still "make tinderbox" clean.
Regen after r268778 to replace WITH_TESTS with WITHOUT_TESTS.
Nuke the never-used RF_TIMESHARE feature, reducing the complexity of the
code.  The consensus on arch@ is that this feature might have been useful
in the distant past, but is now just unnecessary bloat.

The int_rman_activate_resource() and int_rman_deactivate_resource()
functions become trivial, so manually inline them.

The special deferred handling of RF_ACTIVE is no longer needed in
reserve_resource_bound(), so eliminate the associated code at the
end of the function.

These changes reduce the object file size by more than 500 bytes on i386.

Update the rman.9 man page to reflect the removal of the RF_TIMESHARE
feature.

MFC after:	2 weeks
Correct the name of the man page for pmap_ts_referenced().

Sponsored by:	EMC / Isilon Storage Division
Deprecate m_act.  Use m_nextpkt always.
Oops - somehow I missed the IP option numbers clashing with the multicast
numbers below.

Move them to a new set of non-clashing numbers.
Fix a typo.

PR:		191898
Submitted by:	vsjcfm@gmail.com
units(1): Add support for output-format
	Add support for the output-format argument.  This also exposes subtle
	rounding differences between GNU units and our units.
chown: Fix chown test number
units(1): Add basic tests
	Add some tests to help avoid breaking units
Fix ctld crash on startup if target alias is not set.

MFC after:	3 days
Fix embarassing typos I made.

Submitted by:	rayddteam
grep: Fix type.

Obtained from:	NetBSD (CVS rev. 1.17)
MFC after:	3 days