RFR: Merge remaining jdk11

[Roman Kennke]

This merges from jdk/jdk up to:

changeset:   50805:ec70aad8aebe
user:        simonis
date:        Fri Jun 08 10:22:26 2018 +0200
summary:     8204335: [ppc] Assembler::add_const_optimized incorrect for
some inputs


There've only been smallish stuff, and a bunch of improvements that I
pushed to upstream meanwhile.

Testing looks good, except that StringInternCleanup.java appears to
trigger a bug in concurrentHashMap when run from fastdebug. I hope
Zhengyu can look at that?

List of changesets:
http://cr.openjdk.java.net/~rkennke/upstream-merge-2018-06-08/outgoing.txt

Ok?

Roman