add semantics for @nogc
Merge pull request #3490 from WalterBright/more-nogc

DIP60: add semantics for @nogc
small refactor
Merge pull request #3494 from WalterBright/refactor-isNogc

small refactor
Fix Issue 11620 - Emit enum member values to json output.
Merge pull request #3472 from AndrejMitrovic/Fix11620

Issue 11620 - Emit enum member values to json output.