Don't try to clone floats, nil, true, or false.
Add tests for cloning dates and times.
Add tests for cloning Regexps.

Includes a failing test; /regexp/.clone is not allowed normally, but
ruby-deepclone does permit this. Regexp.new('regexp').clone should
always be allowed.
Merge pull request #1 from antw/additional-classes
Include the RCLASS_IV_INDEX_TBL macro as it doesnt exist on the ruby includes.
Made it work with frozen objects; Added some debug helpers.
Merge andremedeiros changes