Some small convenience things for emojicode-sys.

Example: ```rust

[macro_use]

extern crate emojicode;

use emojicode::*;

package_version!(0, 1);

emojifunctions!( ehello(thread) { thread.returnfromfunctionwithvalue( String::from("Hello from Rust!") .to_value() .unwrap() ); } );

prepare_class!( (class, name) { println!("{}", name); } ); ```