Add basic per Material scissor testing

It is now possible to enable and specify scissoring on a per
Material basis using getAdditionalRenderState().
Add support for scissor intersections

If a per Material scissoring is specified the resulting scissor area
will be the intersection of that scissor rectangle and any
existing scissor rectangle applied with setClipRect()
Add per Material scissoring support to all Renderers

The per Material scissoring support is now included in the remaining
Renderers.