Note docbook change before new pkg upgrade

[John Marino]

I just updated packages for Release 3.6 (x86_64).
In it is a big change with a "docbook" reorganization.
It will probably break when you try to update via package, so follow
these UPDATING instructions from FreeBSD first.

===================================================
20140219:
AFFECTS: users of textproc/docbook*
AUTHOR: mat at FreeBSD.org

The textproc/docbook-* ports have been consolidated into two ports
textproc/docbook-sgml and textproc/docbook-xml.

Before upgrading you should force the removal of the existing ports, they
will conflict with the new ones.

pkg users can run:

pkg delete -f docbook-xml\* docbook-sk\* docbook\[2345\]\?\?-\* docbook-4\*
=======================================================

I'm torn about copying "UPDATING" because a some point in the not too
far off future "pkg" should be able to automatically handle cases like
this.  In any case, we currently don't have an UPDATING file in DPorts.

John