Cleaning up a few places in the code

[akukanov]

A couple of changes lurking in my working copy, plus the changes for unused variables from #471 that still apply, and dropping colons before std in the code around.

[SergeyKopienko]

@akukanov I think technically this patch is OK.
But is it a good practice to mix some significant changes like remove unused param from __parallel_transform_scan_base together with some unsignificant changes like remove :: in one PR?

[akukanov]

@akukanov I think technically this patch is OK. But is it a good practice to mix some significant changes like remove unused param from __parallel_transform_scan_base together with some unsignificant changes like remove :: in one PR?

We have decided in the past that we will gradually remove :: as we update the code base, Essentially, I removed it from the functions & classes touched by the more significant changes - but yes, it's somewhat wider than only the modified expressions. Since the whole patch is about cleaning up the code without any functionality add or loss, I tend to think it's OK.

Update: it seems the changes in __parallel_copy_if only consist of the colon removal. That's accidental, but I do not think it makes much sense to revert these 4 changed lines.

[SergeyKopienko]

LGTM