Bug 2087 – Merge stc.typecons.defineEnum with enum

I find that nearly (if not) every enum in my code is defined using std.typecons.defineEnum for the toString() and fromString() functionality. I'd suggest moving this into the language itself. Like Objects, an enum will have a .toString property which does exactly what is defined on the defineEnum mixin. The fromString() isn't as important, but since we're at it, why not do the full round? Defining enums with this mixin wrecks chaos on IDE parsers, as I try to use "MsgType" as a variable type and the IDE's parser never knows of it.

enum is not a class, there will not be enum.toString. Nevertheless, std.conv.to supports converting between an enum and string for a number of versions already. std.typecons.defineEnum has also been deprecated.