Go back to a State::new() instead of deriving Default
Go back to a State::new() instead of deriving Default

Sigh, I am moving the affine field into the Rust State struct, but
cairo::Matrix doesn't impl Default.  So, do this by hand again.

See https://github.com/gtk-rs/cairo/pull/180 for impl default fro Matrix

GNOME/librsvg,GNOME/librsvg,GNOME/librsvg,GNOME/librsvg