Multiple changes.
- Remove the runtime dependency on rake-compiler.
- Use #rb_str_new instead of #rb_str_new2, the hash character array
isn't null terminated.
- Add various safeguards for object instantiations.
- Remove the 'threaded' options for messages, folding them into
'archived'. If archiving is enabled, so is threading.
- Return nil for lookups from the list object instead of raising
exceptions.
- Open subject indexes with the proper encodings (thanks Michael
Granger!)
- Allow touching and unlinking files to operate on multiple paths
at once, within a single safety() wrap.