* Update `.clang-format` defaults.
* Enable `AlignConsecutiveMacros`, newly supported by clang-format 9.
We often followed this style before using clang-format, and I believe
that it produces generally positive changes.
* Apply clang-format changes.
* Replace `_FITS` and `_NEXT_ALIGN` macros. clang-format didn't damage
them, it just brought them to my attention. These macros weren't
improving clarity, and the code is more systematic without them.
(For the time being, I have refrained from further overhauling the
metaprogramming here.)
Add jobify.exe and parallelize.exe
Add a "tools" directory for test/build support tools.
Add jobify.exe from the msvc repo.
Extract parts of jobify into stljobs.h, and author wrappers for other test support.
Add parallelize.exe which runs a command in parallel over all inputs in a directory.
Teach Azure DevOps to enforce clang-format in parallel.