Much renaming and refreshing of RBE

rustbyexample/hello.d/print.d/print_display.rs

@@ -0,0 +1,14 @@
+use std::fmt;
+
+struct Structure(i32);
+
+impl fmt::Display for Structure {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+fn main() {
+    let s = Structure(4);
+    println!("s={}", s);
+}