* Change to using per-thread timers
* fix bad assertions
* fix copy paste error on windows
* Fix thread safety annotations
* Make null-log thread safe
* remove remaining globals
* use chrono for walltime since it is thread safe
* consolidate timer functions
* Add missing ctime include
* Rename to be consistent with Google style
* Format patch using clang-format
* cleanup -Wthread-safety configuration
* Don't trust _POSIX_FEATURE macros because OS X lies.
* Fix OS X thread timings
* attempt to fix mingw build
* Attempt to make mingw work again
* Revert old mingw workaround
* improve diagnostics
* Drastically improve OS X measurements
* Use average real time instead of max
This patch does two things:
1. It overhalls the static initialization in Walltime to be simplier. It uses
a static variable inside WallTime::Now() to initialize the timer.
2. Add a logging mechanism so that the -v flag actually has meaning and
reimplement the CHECK macros to allow extra messages to be streamed in.
