Joni regexp patch

[Hannes Wallnoefer]

I've uploaded a patch for using a modded Joni regexp engine (the regexp 
library from JRuby) with Nashorn:

http://cr.openjdk.java.net/~hannesw/8006028/

This passes test and test262parallel, and it speeds up the Octane regexp 
benchmark almost 2x. Joni code adds about 180kb to the size of nashorn.jar.

The patch moves Joni classes into package jdk.nashorn.internal.joni. 
Otherwise the code is identical to the "noencoding" branch on my github 
Joni fork where I have removed the dependency on the jcodings library 
and added some JavaScript support.

https://github.com/hns/joni/tree/noencoding

I guess there are some things to be considered with a patch this size. 
Looking forward to the discussion!

Hannes