core: correct the u64/s64 data types and remove STRINGIFY.
core: put typedefs of int/char/... in global space.

Conflicts:
	src/graphics/src/opengl/mesh_opengl.cpp
input: InputEvent class added to be emitted on input events.

InputEvent derives from the Event class and offers a key() method that
returns the key that was pressed.
demo: changes to reflect the new InputEvent class addition.