support for 2D shadow casters

Added support for 2D shadow casters.

*DANGER* Shaders in CanvasItem CHANGED, if you are using shader in a
CanvasItem and pull this, you will lose them. Shaders now work through a
2D material system similar to 3D. If you don't want to lose the 2D
shader code, save the shader as a .shd, then create a material in
CanvasItem and re-assign the shader.

core/variant_op.cpp

@@ -552,6 +552,9 @@ void Variant::evaluate(const Operator& p_op, const Variant& p_a, const Variant&
 					if (p_b.type==MATRIX32) {
 						_RETURN( *p_a._data._matrix32 * *p_b._data._matrix32 );
 					};
+					if (p_b.type==VECTOR2) {
+						_RETURN( p_a._data._matrix32->xform( *(const Vector2*)p_b._data._mem) );
+					};
 					r_valid=false;
 					return;
 				} break;