The scene now owns its renderer, so there is no need to keep a list
of existing renderers and to call Renderer::Get().

Let’s be honest, I’m never gonna use it in its current form.

We used to have lol::map::empty() to empty maps, but in std::map
this method is called clear(). It sounds safe to harmonise between
our types and have lol::array::clear() too.

debug draw fixes are really un-numerous in ze lol, it seems

getter default params are better now

Next pass is clean-up and fix of all the old usage

We have no hope of extending lua_State to add more data to it, because
that object may be created by Lua itself, for instance within a coroutine,
and it has no knowledge of our version of the object.

For now the flags are: --disable-doc --disable-test
--disable-samples --disable-tutorial.

All these changes will allow us to more easily add Lol Engine as a
submodule of another Git project.

We already have the convenient degrees() and radians() functions to convert
between angle formats. This commit involves a lot of refactoring here and
there and I may have missed some places where conversions were needed. But
hopefully there aren’t may such places.

This lets us use the code for non-float variable types. I also got
rid of the mat4-to-quat code so that users are forced to use the
mat3-to-quat code and possibly discover places where their code is
suboptimal.

Using “Array” instead of “array” is now fully deprecated, and I replaced
the Log::Debug() etc. functions with msg::debug() etc. because log:: was
unavailable due to being a maths function.

Added up-to-date copyright notice and BOM to modified files, just in case.

The containers no longer force the user to use the ptrdiff_t type for
size information. For convenience, size() now always returns an int,
and the size_s() method offers a way to handle arrays with more than
2 billion elements. Internally, we still use ptrdiff_t, though.

Since so much code had to be changed, I took the opportunity to get
rid of capitalised accessors for classes that are lowercase.

Though it still is not possible to create a new window from a thread that did not init SDL