Fix sizeclass rounding error

Merge pull request microsoft#172 from microsoft/callback-fixes

Callback fixes

Addressing OE linking issues when built with GCC (microsoft#167)

* Use C++17 inline statics

This leads to better codegen in GCC, and fixes some linking issues in OE.

* Detect GCC and OE combination and fall-back to lock based ABA.

* clangformat

Merge pull request microsoft#102 from microsoft/cq-free

Code quality for `free`

Merge pull request microsoft#59 from plietar/paper

Add paper.

Merge pull request microsoft#21 from plietar/smart-next

Place the next pointer at a different place on every object.