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.