Commit c033dd8a3e8f58f307d3e248a68b62252d3fc2c6

Edward Thomson 2021-11-06T16:14:47

cmake: standardize USE_THREADS and USE_NSEC Threading can now be disabled with `USE_THREADS=OFF` instead of `THREADSAFE=OFF` to better support the other cmake semantics. Nanosecond support is the default _if_ we can detect it. This should be our default always - like threads - and people can opt out explicitly.