RFR: 8213569: Bump minimum boot jdk to JDK 11

[Mikael Vidstedt]

Please review this change which bumps the minimum boot jdk to JDK 11 (see [1] for Boot-JDK policy).

bug: https://bugs.openjdk.java.net/browse/JDK-8213569 <https://bugs.openjdk.java.net/browse/JDK-8213569>
webrev: http://cr.openjdk.java.net/~mikael/webrevs/8213569/webrev.00/open/webrev/ <http://cr.openjdk.java.net/~mikael/webrevs/8213569/webrev.00/open/webrev/>

* Background

JDK 11 is now GA. The minimum boot JDK version for mainline/JDK 12 should be bumped.


In addition to bumping the minimum boot JDK version this change also updates the boot JDK used by the Oracle build system.

* Testing

tier1-3 (found one unrelated/known failure).

Cheers,
Mikael

[1] http://mail.openjdk.java.net/pipermail/jdk-dev/2018-April/001075.html <http://mail.openjdk.java.net/pipermail/jdk-dev/2018-April/001075.html>