Fix another test broken by move.
Fix an ungetc test to match MRI and JRuby to pass it.
Remove ungetc tests covered elsewhere. They don't pass MRI either.
ByteList fix and minor tweaks to setStrBuf to fix large reads.
Sprinkle a little fairy dust and synchronization on IO.
Missing write_lock logic, though we're not using it right now.
Hide these methods.