RFR: JEP 359-Records: compiler code

[Brian Goetz]

This doesn’t work when you invoke the tests through `make run-test`, which is why I used the explicit 14.  

> On Oct 22, 2019, at 11:21 AM, Jan Lahoda <jan.lahoda at oracle.com> wrote:
> 
> -for tests, "--enable-preview -source 14" is used on many places. This will cause issues when JDK 15 is started (and --enable-preview -source 14 will be replaced with --enable-preview -source 15). On all places where that is possible, "--enable-preview -source ${jdk.version}" should be used, or a programmatic equivalent.