Fix the mdbm library to compile correctly on the redhat71 platform.  Also add a t.mdbm regression test that tests the library.
Fix the mdbm library to compile correctly on the redhat71
platform.  Also add a t.mdbm regression test that tests
the library.

bk: 411104a1N3nndAcPcLxu2w9MEs1uMQ
bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper