Introducing sysupgrade

[Julio Merino <jmmv%NetBSD.org@localhost>]

Hello,

Following my previous announcement of sysbuild, I'm introducing
sysupgrade today (pkgsrc/sysutils/sysupgrade).

sysupgrade is a script to, as you can guess, automate the upgrade of a
live NetBSD system to a newer release based on distribution sets.  I'm
not going to say much more in this email as the following two links
contain much more details:

    http://mail-index.netbsd.org/pkgsrc-changes/2012/08/06/msg076544.html
    http://julipedia.meroh.net/2012/08/introducing-sysupgrade.html

What I would like to clarify here is that, since the addition of
sysbuild, I was made aware of the companion scripts included in
etcmanage.  However, I have moved forward with sysupgrade anyway for a
variety of reasons -- mostly because I had it written already, but
there are others as mentioned in the commit message ;-)

Feedback and testing welcome.

Enjoy!