dmd: Encourage more inlining across modules

[Adam D. Ruppe]

On Thursday, 29 November 2018 at 23:59:55 UTC, Andrew Pennebaker 
wrote:
> I read from the FreeBSD documentation that dmd can compile many 
> source trees without having to explicitly list all the 
> filenames, however a lot of inlining optimizations are missed.

Where, exactly, does it say that? The only possibility I can find 
is the -i option, but that works basically the same way as 
explicitly listing them.