* Servers now use WorkerThreadPool for background computation.
* This helps keep the number of threads used fixed at all times.
* It also ensures everything works on HTML5 with threads.
* And makes it easier to support disabling threads for also HTML5.
CommandQueueMT now syncs with the servers via the WorkerThreadPool
yielding mechanism, which makes its classic main sync semaphore
superfluous.
Also, some warnings about calls that kill performance when using
threaded rendering are removed because there's a mechanism that
warns about that in a more general fashion.
Co-authored-by: Pedro J. Estébanez <pedrojrulez@gmail.com>