Rename simple_math() to i64_math()

src/jit/engine.rs

@@ -82,7 +82,7 @@ mod tests {
     }
 
     #[test]
-    fn simple_math() {
+    fn i64_math() {
         let source = "simple_math() i64 { (1 + 2) * ((4 + 5) / 3) }";
         let code_fn = jit_fn::<(), i64>(source);
         assert_eq!(code_fn(()), 9);