[Issue 17985] Implement -stdin for rdmd

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=17985

hsteoh at quickfur.ath.cx changed:

           What    |Removed                     |Added
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                 CC|                            |hsteoh at quickfur.ath.cx

--- Comment #1 from hsteoh at quickfur.ath.cx ---
Doesn't rdmd already have --eval for this purpose?

Of course, being able to read from stdin has its own value (e.g., run rdmd on
output produced by some code generating program via stdin, without needing to
create a temporary file).

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