Import mdocml-1.13.1
Merge branch 'vendor/MDOCML'

Conflicts:
	contrib/mdocml/Makefile
	contrib/mdocml/mandoc.h
	contrib/mdocml/mdoc_validate.c
	contrib/mdocml/read.c
mdocml: compile and reapply some local changes
powerd: add an option to disable turbo mode
Remove various pkgsrc remains.

* Remove pkgsrcaudit periodic script.

* Remove pkg_radd(1) and pkg_search. pkg(8) will do.

* Remove pkgsrc(7) manual page.

* Remove test/fastbulk (meant to be a faster alternative to pbulk but it
  never took off).

* Remove searching of /usr/pkgsrc searching via whereis(1).

* Various small adjustments.
powerd.8: Fix a typo and elaborate a bit on what -t means.
Remove pkg_radd from the Makefile too.
powerd: add tunables to control the load thresold
powerd.8: Fix incomplete -p / -u commit.
rc.8: Mention 'reload', which is enabled frequently to kill -HUP daemons.

Reported-by: Matteo Cypriani <mcy@lm7.fr>
kern/dsched: Fix a panic at proc exit

 * When a proc exit, dsched tries to destroy the thread context.
   But if the thread context is not empty, it needs to wait
   for the thread ios to be drained.

 * add a callback to wakeup the thread when the last queued io is
   completed and resume the in progress destruction.

 * Should fix #2645