MFC 257006

sbin/geom/class/part/geom_part.c
        Always validate the return of find_geomcfg().  It could be NULL, for
        example when the geom is withering.

Approved by:    ken (mentor)
Sponsored by:   Spectra Logic Corporation
MFC 256640:  Allow 'make xdev' to work when DESTDIR is set.
MFC r256647:

  Invalidate the entire L2 cache before enabling it.  Say whether it
  has been enabled or disabled.
MFC r256774:

  Clock divisors 0-3 correspond to dividing by 1-4, so add 1 before dividing.
MFC r256804:

  Switch to using the standard uart console driver instead of the special
  driver for early boot debugging.
MFC r257130:

  Add a helper routine to search for a compat string in a table that
  associates compat strings with arbitrary values that mean something to
  the driver.  This is handy for drivers that support several variations
  of similar hardware and need to know which one matched.