Implement Copy on Fill and Stroke

[vladh]

In general, would it not be better to have functions such as fill_rectangle take &Fill to prevent unnecessary copies, especially when drawing the same item over and over?

[hecrj]

Premature optimization. Compilers are smart and dereferencing could potentially be slower.

In any case, the cost of a copy is negligible when compared to the actual tessellation. So, why bother with these questions?