Adding in Don Anderson's implementation of the 3n+1 benchmark. This should compliment the micro benchmark tests as a way to gage release over release performance changes.

Author: Gregory Burd

test/3n1/README

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+https://github.com/ddanderson/libdb-3n
+
+This code implements the 3n+1 benchmark.  A description of the benchmark and results is on the libdb blog here:
+  http://libdb.wordpress.com/2011/01/31/revving-up-a-benchmark-from-626-to-74000-operations-per-second/