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.

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

This branch seems pretty stable, and it lets us get rid of some
legacy code about extensions.

bullet3, pegtl: update upstream branches.
imgui: add missing files in “make dist”.

imGui docking extension tweak
tileset new getters

Added scissor mode in renderer
Added scissor support in imGui
Mouse scroll sensivity tweak

small imgui extension
scene palette shader crashfix

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

Seems to still build in lol, will check other works to be sure

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

- removed 0 CR characters
 - removed 7 trailing whitespaces
 - replaced 332 tabs with spaces

- Most recent version is in with index buffer support

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

Reworked Primitive logic for scene rendering
FileUpdateTester works now .....

MeshViewer first pass

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

Added Texture (by image) update in TextureImage (and tileset)
Added lolimgui first integration pass