Update E0124 to the new error format

src/test/compile-fail/E0124.rs

@@ -9,8 +9,10 @@
 // except according to those terms.
 
 struct Foo {
+    field1: i32, //~ NOTE `field1` first declared here
     field1: i32,
-    field1: i32, //~ ERROR E0124
+    //~^ ERROR field `field1` is already declared [E0124]
+    //~| NOTE field already declared
 }
 
 fn main() {

src/test/compile-fail/struct-fields-decl-dupe.rs

@@ -9,8 +9,10 @@
 // except according to those terms.
 
 struct BuildData {
+    foo: isize, //~ NOTE `foo` first declared here
     foo: isize,
-    foo: isize, //~ ERROR field `foo` is already declared
+    //~^ ERROR field `foo` is already declared [E0124]
+    //~| NOTE field already declared
 }
 
 fn main() {