The number of templates instantiated when doing just `import std; ` is too damn high

[Andrei Alexandrescu]

I mean take a look: https://run.dlang.io/is/ZA16nq

https://issues.dlang.org/show_bug.cgi?id=21907

Ideally there should be virtually no work done when the standard 
library is imported but not used.

First step:

https://github.com/dlang/phobos/pull/8053