RFR: JDK-8133680 add Stream.foldLeft() terminal operation

[Tagir Valeev]

Please review the preliminary implementation for Stream foldLeft and
foldRight operations:

http://cr.openjdk.java.net/~tvaleev/webrev/8133680/r1/

This implementation has no tests yet. Before writing them I'd like to
be sure that this enhancement could be accepted in general (or
probably foldLeft is accepted and foldRight is not?) Could anybody
sponsor it when it will be complete?

Thank you in advance!

Tagir Valeev.