RFR(m): 8139233u1 add initial compact immutable collection implementations

[Stuart Marks]

Hi all,

Here's a revised webrev, incorporating some of the comments from Peter Levart, 
Stephen Colebourne, and Rémi Forax.

http://cr.openjdk.java.net/~smarks/reviews/8139233/webrev.1/

I'd like to proceed with this changeset mostly as-is, and to allow discussion of 
other issues (such as spec changes regarding iteration order) to proceed 
asynchronously.

Thanks,

s'marks