JDK 13 RFR of JDK-8205626: Start of release updates for JDK 13

[joe darcy]

Hello,

With JDK 13 inception right around the corner, please review the 
langtools portions of

     JDK-8205626: Start of release updates for JDK 13
     http://cr.openjdk.java.net/~darcy/jdk13-fork.2

which include fixes for the bugs

     JDK-8205393: Add SourceVersion.RELEASE_13
     JDK-8205394: Add source 13 and target 13 to javac
     JDK-8214825: Update preview language features for start of JDK 13

The changes to add SourceVersion.RELEASE_13 and the new -source/-target 
value are analogous to corresponding updates in earlier releases. Given 
the mechanisms used to implement the policies of JEP 12: "Preview 
Language and VM Features" (http://openjdk.java.net/jeps/12), in the 
tests for the preview language features many "12"s had to updated "13"s. 
We may look to streamline how such edits need to occur in future releases.

With this set of changes, the langtools regression tests pass cleanly. 
The build changes are being reviewed separately 
(http://mail.openjdk.java.net/pipermail/build-dev/2018-December/024285.html) 
and the core libs and hotspot changes will have their own threads once 
those changes are further along.

Thanks,

-Joe