Establish OpenJDK upstream for remaining java.util classes.

The corresponding OpenJDK upstream commit is the same as
for java.util.concurrent [1]. Thus, this CL results in the
difference between the old and new upstream being applied to
ArrayPrefixHelpers.java.

Previous commit messages [2] suggesting that the other files
listed below were at the time directly derived from JSR-166
may have been incorrect.

All Android changes (removed link to collections framework docs;
fix framework docs link to "Collection#optional-restrictions")
are kept, as indicated by comments in the files.

This CL also fixes up some redundant missing/extra blank lines
that appeared to needlessly differ between Android and both
upstreams.

The set of classes in java.util that are contained in JSR-166
and mentioned by [2] but for which the OpenJDK upstream [1] is
now established are:

 - ArrayDeque (removed a needless "E" that differed from both
   upstreams)
 - ArrayPrefixHelpers (newly moved to OpenJDK upstream [1])
 - Deque
 - Map (no changes required, not touched by this CL)
 - NavigableMap
 - NavigableSet
 - PriorityQueue (no changes required, not touched by this CL)
 - Queue
 - SplittableRandom

Classes from java.util not on the above list are derived from
a different upstream revision such as OpenJDK8u60.

[1] between jdk-9+113 and jdk-9+114, as described in
    http://r.android.com/304056 (libcore commit
    29957558).
[2] commits fd81a994
    and e8b323c7
    in libcore

Test: make
Bug: 30860904
Bug: 29935305
Change-Id: I46b19ce8afd6467d1134beeb6f3d7f5ebc09f8fa