RFR 8017447 Unmodifiable map entry becomes modifiable if taken from a stream of map entries

[Paul Sandoz]

Hi,

Please review a patch that fixes traversal of unmodifiable map entry set where 
entries could be set:

  http://cr.openjdk.java.net/~psandoz/tl/JDK-8017447-unmod-map/webrev/jdk.patch

This covers forEach, spliterator (splitting, tryAdvance, forEachRemaining), 
iterator forEachRemaining, stream/parallelStream forEach with instances of Map 
and SortedMap.

Note that there are other changes which will follow later on to Collections 
that update implementations with stream/parallelStream methods

Paul.