Bug#714788: switch to faster kyotocabinet instead of gdbm

[Shawn]

Package: mailutils
Severity: wishlist
gdbm is really slow http://tokyocabinet.sourceforge.net/benchmark.pdf
kyotocabinet is available

switch --with-gdbm to --with-kyotocabinet and build-depend on
libkyotocabinet-dev
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Shawn Landden