Add only_i32 and only_i64 features.

tests/comments.rs

@@ -1,14 +1,14 @@
-use rhai::Engine;
+use rhai::{Engine, INT};
 
 #[test]
 fn test_comments() {
     let mut engine = Engine::new();
 
     assert!(engine
-        .eval::<i64>("let x = 5; x // I am a single line comment, yay!")
+        .eval::<INT>("let x = 5; x // I am a single line comment, yay!")
         .is_ok());
 
     assert!(engine
-        .eval::<i64>("let /* I am a multiline comment, yay! */ x = 5; x")
+        .eval::<INT>("let /* I am a multiline comment, yay! */ x = 5; x")
         .is_ok());
 }