SDL_helpers: Fix SDL_Rect(IntRect) method variant
Rect: Remove reference aliases & rename width->w & height->h

* Using reference aliases in the class like so was potentially
dangerous, and so the fix I’ve decided on is to simplify things here.
Texture: Add support for update_area argument of update method
Texture: Introduce TextureAccess enumeration

* Reserved for ease of future expansion; mirroring SDL2 texture types
in the mean time.
Point2: Remove reference aliases w & h — change class to struct

* Using reference aliases in the class like so was potentially
dangerous, and so the fix I’ve decided on is to simplify things further
like so.
Point3, Rect: Change class to struct

Nothing to see here, move along … purely semantic 
Texture, Image: Replace Coords data type with IntRect
More IFont, Label, Glyph refactoring
examples/fonts: Disable loading of small bitmap font
Coords: Rename width, height to w & h — remove reference aliases

* Using reference aliases in the class like so was potentially
dangerous, and so the fix I’ve decided on is to simplify things
further like so
Fix linking err (missing typeinfo, vtable)
Image: Introduce clone method
Transformable: Rename getSize method & return reference to Coords
More IFont, Label, Glyph refactoring