D Editions

[Richard (Rikki) Andrew Cattermole]

We're briefly discussing editions on Discord and complexity of 
implementation where I'm making the note that some of the infrastructure 
and one change is already applied.

However a point I want to make is in the implementation there is a 
legacy version along with 2024.

https://github.com/dlang/dmd/blob/15f66f89c9d80bbd71274f272e58c273684905ee/compiler/src/dmd/astenums.d#L22

This is a point I've previously made that the base version (aka legacy) 
should be given the version number 2 and should not have DIP1000 enabled 
for it.