upgrading to new releases. Important parts of this code include
* automatically determining which optional components (e.g., src,
info, proflibs) are installed.
* merging changes in files which are modified locally and have
changed between the currently running and new release.
* prompting the user to rebuild all 3rd party software before
deleting old shared libraries.
Yes, this is compatible with "freebsd-update rollback" -- you can
test a new -BETA and roll back to the old release if you don't
like it.
Subject to re@ approval, this will be MFCed before 7.0-BETA3 and
6.3-RC1.
MFC after: 2 days
e1798e6b44