[11u] RFR (Backport): 8223553: Fix code constructs that do not compile with the Eclipse Java Compiler

[Langer, Christoph]

Hi,

I'd like to bring this fix down to jdk11 updates. Unfortunately, the webrev did not apply cleanly in the imports section of src/java.net.http/share/classes/jdk/internal/net/http/ExchangeImpl.java, so I had to resolve this part manually. I also updated the copyright year. Please check.

Webrev: http://cr.openjdk.java.net/~clanger/webrevs/8223553.11u/

Thanks
Christoph