RFR: jsr166 jdk integration 2018-01

[Martin Buchholz]

http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/overview.html

8191483: AbstractQueuedSynchronizer cancel/cancel race
http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/AQS-cancel-cancel-race/index.html
https://bugs.openjdk.java.net/browse/JDK-8191483

Lots of minor changes inspired by code analysis tools:

8193300: Miscellaneous changes imported from jsr166 CVS 2018-01
http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/miscellaneous/index.html
https://bugs.openjdk.java.net/browse/JDK-8193300