RFR: JDK-8012542 (Stream methods on Collection)

[Brian Goetz]

Updated spec for Collection.spliterator; default methods for 
Collection.stream() and parallelStream().  Specialized implementations 
in subtypes will come in a separate putback.

Webrev at:
  http://cr.openjdk.java.net/~briangoetz/JDK-8012542/webrev/