Added comments and did a tiny bit of cleanup to help understand a bug we currently have with multiple threads hitting breakpoints. Mostly comments and log changes. Any other changes should cause no semantic difference, and are for clarity only.
Differential Revision: D943943
C++11 cleanup (clean up easy enums)
This is for runtime/base/... and ended up touching a lot of files
because it turns out we have a lot of reasonably behaved enums.