Phobos: Clean up LDC-specifics in std.math

[kinke]

No description provided.

[smolt]

Just out of curiosity to improve my feeble brain. This PR is referring to a commit on a phobos PR branch. Do you have to redo it after the phobos PR is merged? Otherwise it would be referring to a commit not the the ldc branch, right?

[kinke]

I don't really know. :)
I created a Phobos branch on the official remote so that I can test it with this LDC-PR. I'm not sure whether I can just transplant (cherry-pick?) the single Phobos commit to the ldc branch, keeping its hash (in case there are no further changes on the ldc branch). In that case, I could just merge this PR; otherwise, I'll have to push a new commit to LDC master (or rebase this PR).
I don't know what the better approach is - merging the Phobos-PR and pushing a LDC commit or doing it the other way around, pushing to Phobos and merging an LDC-PR. Ideally, we'd 'just' ;) have proper CI tests for druntime and Phobos too.

[kinke]

Already merged in, closing.