This fixes a lost wakeup in SPSCQueue. If the reader is in just the right position, the writer's notification will be lost and this will be a problem if the writer then does something to wait on the reader.
This was discovered to affect my upcoming stacktrace PR. I don't think any performance decrease will be noticeable because an uncontended mutex is smart enough to skip the syscall. This PR might also resolve some rare deadlocks but I don't know of any examples.
Since C++17, the introduction of deduction guides for locking facilities
means that we no longer need to hardcode the mutex type into the locks
themselves, making it easier to switch mutex types, should it ever be
necessary in the future.
Makes it consistent with the regular standard containers in terms of
size representation. This also gets rid of dependence on our own
type aliases, removing the need for an include.
The necessity of this parameter is dubious at best, and in 2019 probably
offers completely negligible savings as opposed to just leaving this
enabled. This removes it and simplifies the overall interface.
