* Change reinterpret_cast -> static_cast wherever possible
* Remove more unnecessary `const_cast`s.
reinterpret_casts should be avoided for the same reason as c-style casts - they don't do any type-checking. reinterpret_cast was mainly being used for down-casting in inheritance hierarchies but static_cast works just as well while also making sure that there is actually an inheritance relationship there.
Fixes#4040
* The TCP connection is now shutdown after OnBodyFinished
* Any open connections are closed when cNetworkSingleton::Terminate() is called.
* Removed ownership cycles in cUrlClientRequest
* Added a check to the test to ensure there are no leaks.
* SelfTests: Added a cEvent stress-test.
* cNetwork: Fixed startup event hang.
The original code used to hang with a ~ 1:50000 chance, because on Linux the cEvent was destroyed before its "Set()" returned.
