[Issue 12758] allow file names with hyphens

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=12758

--- Comment #5 from Tom Browder <tombrowder at acm.org> ---
> Isn't it simpler to rename the file "test_bu.d"?

Simpler, but I'm looking at dealing with a large C/C++ code base and many files
are named using hyphens.  I know it may be easier to rename the file but I
still think the capability should be there.

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