Revert "Refine examples."

This reverts commit 146129279c.

examples/arrays_and_structs.rs

@@ -1,6 +1,3 @@
-#![cfg(not(feature = "no_index"))]
-#![cfg(not(feature = "no_object"))]
-
 use rhai::{Engine, EvalAltResult};
 
 #[derive(Debug, Clone)]
@@ -17,6 +14,8 @@ impl TestStruct {
     }
 }
 
+#[cfg(not(feature = "no_index"))]
+#[cfg(not(feature = "no_object"))]
 fn main() -> Result<(), Box<EvalAltResult>> {
     let mut engine = Engine::new();
 
@@ -47,3 +46,8 @@ fn main() -> Result<(), Box<EvalAltResult>> {
 
     Ok(())
 }
+
+#[cfg(any(feature = "no_index", feature = "no_object"))]
+fn main() {
+    panic!("This example does not run under 'no_index' or 'no_object'.")
+}