Remove special casing for some meta attributes

Descriptions and licenses are handled by Cargo now, so there's no reason
to keep these attributes around.

src/libgraphviz/lib.rs

@@ -267,7 +267,6 @@ pub fn main() {
 #![experimental]
 #![crate_type = "rlib"]
 #![crate_type = "dylib"]
-#![license = "MIT/ASL2"]
 #![doc(html_logo_url = "http://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "http://www.rust-lang.org/favicon.ico",
        html_root_url = "http://doc.rust-lang.org/nightly/")]