JRuby support

[headius]

Add support for RBTree on JRuby.

[headius]

This will solve knu/sorted_set#7 once complete.

[mame]

Please let me know when your patch is ready. Since this is a very large code addition, I would like to ask the author and maintainer, OZAWA Takuma, to make a decision. I am just helping him, and this public mirror repository is just for minor fixes and to make it easier for me to do the release work.

BTW, is there an option to distribute it as a separate gem, such as rbtree-java gem? (I am not familiar with JRuby's gems)

[headius]

I managed to get a lot of this implemented, but the methods that expose red/black tree internals are a bit harder to emulate atop this library. Example: left/right boundaries, shift and pop... difficult to implement given the complexity of this concurrent red/black tree impl.

A port of the C dict logic would obviously map exactly, but not have the same concurrency characteristics.