OpenGL includes are ~35k lines together and it is a waste of
compilation time to include them even if they are not needed at all
(e.g. whole SceneGraph and Physics libraries). Saves ~10s of compilation
time (6:46 before, now 6:35).
It prevents unwanted implicit conversions from e.g. nullptr to Camera,
Vector2 to Physics::Point etc. By making all the constructors explicit
it is easier to routinely add the keyword to all new classes instead of
thinking about cases when to add and when not to.
We still want to target old Intel machines with OpenGL 2.1. Also moved
important information from constructor documentation to class
documentation. Who would look into constructor documentation for that?
Because with NaCl WindowContext doesn't make sense anymore, the classes
are now renamed:
* Contexts namespace -> Platform
* *WindowContext -> Application
Hopefully this is (one of) last crazy renaming runs.
If being careful, it's now possible to swap GlutContext with EglContext.
GlutContext doesn't have keyReleaseEvent() and many keys, but EglContext
doesn't have e.g. mouseMotionEvent().