[Issue 19028] Emit warning for identifiers starting with `__`

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19028

Steven Schveighoffer <schveiguy at yahoo.com> changed:

           What    |Removed                     |Added
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                 CC|                            |schveiguy at yahoo.com

--- Comment #1 from Steven Schveighoffer <schveiguy at yahoo.com> ---
My suggestion is to only emit warnings for packages that are not owned by the
language. In other words, the language should be free to add these types of
symbols in std.*, rt.*, core.*, and object without complaint.

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