unused_qualification lint warnings

When running Clippy, there are lots of warnings like
```
warning: unnecessary qualification
--> crates\win-api-wrappers\src\thread.rs:175:54
|
175 | ThreadAttributeType::ParentProcess(_) => mem::size_of::(),
| ^^^^^^^^^^^^^^^^^^^^^^
|
help: remove the unnecessary path segments
|
175 - ThreadAttributeType::ParentProcess(_) => mem::size_of::(),
175 + ThreadAttributeType::ParentProcess(_) => size_of::(),
```

`std::mem::size_of` and `mem::size_of` both fail this lint.

I suggest removing the lint if the maintainers prefer to use `mem::size_of`, or to accept the lint suggestion, i.e., unqualified `size_of`.

I can make a PR for this pending guidance.

#1068 related