ATF use (BIND 9.7.4 is now available)

["Jeremy C. Reed" <reed%reedmedia.net@localhost>]

From the recent BIND announcement:

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Feature Changes

9.7.4

     * Merged in the NetBSD ATF test framework (currently version 0.12)
       for development of future unit tests. Use configure --with-atf to
       build ATF internally or configure --with-atf=prefix to use an
       external copy. [RT #23209]

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