Set default value to -d option (ref #8022)

Reported by pypypy567. Thanks!!!

git-svn-id: http://jp.rubyist.net/svn/rurema/bitclust/trunk@5741 018432c1-2f1c-0410-ba7c-d424024924b7
Use BitClust::MethodDatabase instead of BitClust::Database (Fix #8022)

Reported by pypypy567. Thanks!!!

git-svn-id: http://jp.rubyist.net/svn/rurema/bitclust/trunk@5742 018432c1-2f1c-0410-ba7c-d424024924b7