Controller::WasKeyReleasedThisFrame() is now keyboard->key_released() so
there is usually no need for a controller. They will completely disappear
when joystick axis binding has been ported to InputDevice.

Most input and GUI files are now in a common ui/ directory. The platform/
directory is no longer, as everythyng was moved to application/ or ui/.

In particular, get rid of the enum magic; we can use map<string,int> if we
really need some named enums. Which we usually don’t.

I was arguing that Enter and other keys should be part of the text
input API, but it’s hard to decide what Tab actually does. I prefer
to give more freedom to the client application.

We now just look for SDL2/SDL.h (the regular location) and SDL.h (when
the user provides their own location for this header).

The only reason we had to keep this was for emscripten builds. We can
now use SDL v2 using “emconfigure ./configure CFLAGS="-s USE_SDL=2” and
a few additional flags.

SDL_Mixer v2 is not available in emscripten packages but either it will
be added at some time, or I will get rid of it altogether. An alternate
solution could be this code snippet I found:

    cd SDL2_mixer
    emconfigure ./configure --prefix=$(pwd)/dist --enable-music-ogg --disable-music-ogg-shared CFLAGS="-s USE_VORBIS=1"
    emmake make install

From now on, msg::debug will not display anything, unless this is a debug
build, or the LOL_DEBUG environment variable is set.

Moved ImageLoader to ResourceLoader, so that loading is extensible.
i.e. here: Zed image loader now loads up a tileset instead of being a
hacked image loader.
Goal is to support more funky stuff (wad, pak .....)

sdl integration now supports OS character input as per existing in sdl.
Use SetTextInputActive to turn it off/on

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

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.

SDL2: Mouse is back ! With correct focus support
SDL2: Added typing support with keyboard
ShaderBuilder: Refactored and simplified Shader block creation
Several warning removal
Fixed Image::Copy

scene so that g_scene can be deprecated later.