RFC: JEP JDK-8208089: Implement C++14 Language Features

[Kim Barrett]

I've submitted a JEP for

(1) enabling the use of C++14 Language Features when building the JDK,

(2) define a process for deciding and documenting which new features
can be used or are forbidden in HotSpot code,

(3) provide an initial list of permitted and forbidden new features.

https://bugs.openjdk.java.net/browse/JDK-8208089