The non-const getSkybox() method is especially useful to client code
that needs to change the clear color, but does not have direct
access to the Renderer object.
We're using timed condition variable in one place, but the STL version
pulls in a lot of code because it does clock calculations in
"long double" (!!!!). Since we already had an implementation
of condition_variable, we just add the timed version.
This saves several KiB of code.
Also don't use unique_lock() lock/unlock because it can throw exceptions.
* Clean-up EntityManager a bit
- use tsl::robin_set instead of std::set (which should have been unordered::set
anyways).
- getListeners() now returns a vector which avoids to traverse a set twice.
Turns out that copying the set wasn't as efficient as I thought.
* Improve jobsystem a bit
We recently added a job reference counting mechanism, but we were a bit
too aggressive about taking/release references.
Also make the API more complete by adding explicit retain/release,
which is needed to allow several threads to wait on the same job.
Also improve futex code by inlining it.
* Minor clean-ups
- fix a couple usage of std::function
- fix a couple usage of std::string
- remove ALIGN_LOOP, which didn't work
- fix a couple explicit/noexcept
- virtual -> override
* Fix spelling typos and other minor clang-tidy
