[Mimedefang] two minor doc. errors

[Gary Funck]

At the end of sa-mimedefang.cf:

# Add your own customised scores for some tests below.  The default scores
are
# read from the installed "spamassassin.cf" file, but you can override them
# here.  To see the list of tests and their default scores, go to
# http://spamassassin.taint.org/tests.html .

That URL should read:
# http://spamassassin.apache.org/tests_3_0_x.html

on the assumption that a 2.x.x SA is no longer relevant.

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And in the README file

5. INSTALLATION
---------------

There's an excellent MIMEDefang-HOWTO contributed by Mickey Hill
at http://www.rudolphtire.com/mimedefang-howto/.  It explains
everything in this README in much greater detail. [....]

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The URL is no longer operational. This one works:
http://www.mickeyhill.com/mimedefang-howto/