Fix builds.

src/func/args.rs

@@ -34,6 +34,8 @@ pub trait FuncArgs {
     /// }
     ///
     /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
+    /// # #[cfg(not(feature = "no_function"))]
+    /// # {
     /// let options = Options { foo: false, bar: "world".to_string(), baz: 42 };
     ///
     /// let engine = Engine::new();
@@ -49,6 +51,7 @@ pub trait FuncArgs {
     /// let result: String = engine.call_fn(&mut scope, &ast, "hello", options)?;
     ///
     /// assert_eq!(result, "world42");
+    /// # }
     /// # Ok(())
     /// # }
     /// ```