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

[Stuart Marks]

Hi all,

This is a reimplementation of collections created by the JEP 269 convenience 
factory methods. These implementations are overall quite a bit smaller than 
their conventional collections counterparts, particularly at small sizes. Lookup 
performance for the hash-based structures (Set and Map) is not particularly 
fast, though in most cases it's comparable to TreeSet/TreeMap. Further 
improvements are likely possible.

There are no API changes in this changeset.

Please review:

    http://cr.openjdk.java.net/~smarks/reviews/8139233/webrev.0/

JEP link:

    http://openjdk.java.net/jeps/269

Thanks,

s'marks