[Issue 18961] Need give to compiler/linker' warning/errors some codes (like VC)

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18961

--- Comment #1 from OlegZ <black80 at bk.ru> ---
you can change the error text to something more digestible over time, but the
error code will remain the same, and you can still find old messages about the
error and new ones

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