libc: Fix some warnings.
kernel/ndis: Fix typo in DRIVER_MODULE().
kernel: Use NULL for pointers in DRIVER_MODULE()s.
kernel/isa: Remove redundant check. Already depends on isa per 'files'.
kernel/checkpoint: Fix wrong sizeof (p_sigacts is a pointer).
Makefile.inc: Rework automatic backup (bug 2527)

There were three main problems with the recently added backup feature:
1. It didn't work over NFS
2. It didn't work when a non-root built world the second time
3. It didn't use DESTDIR which had potential to conflict backups

It also previously featured "NO_BACKUP" which turned off the automatic
backup feature.  To fix the #2 problem, the install timestamp has been
removed, so to avoid unwanted backups for multiple installworlds after
one buildworld, the user needs to pass NO_BACKUP in the command line.

This patch was contributed by Thomas Nikolajsen with minor modifications
added by John Marino.

http://bugs.dragonflybsd.org/issues/2527
installer: Make it possible to start the installer from a running system.

Also clean up a little and add a small manual page.

Note that the installer isn't hooked into the normal build/install per
this commit. These changes are mainly to help with testing and debugging.
powerd - Fix load factor calculation bug for niced processes

* A type-o in the load calculation code was not counting niced
  processes at all, so if you have a lot of niced processes
  (like ffmpeg's which nice themselves down), powerd can wind
  up restricting them all to a single cpu.  Doh!
Merge branch 'master' into gsocdrm_github