Consistenly use xxxAtIndex style in List.

Earlier, I only used atIndex where there was name collision.
This resulted in asymetric method names like get vs removeAtIndex.
The patch makes them consistent.

Change-Id: Ie8310cc80ec11d19f1c8c184489a99430fd4d02e
diff --git a/user/super/com/google/gwt/emul/java/util/List.java b/user/super/com/google/gwt/emul/java/util/List.java
index 87e49bf..6107482 100644
--- a/user/super/com/google/gwt/emul/java/util/List.java
+++ b/user/super/com/google/gwt/emul/java/util/List.java
@@ -39,6 +39,7 @@
   @JsMethod(name = "addAllAtIndex")
   boolean addAll(int index, Collection<? extends E> c);
 
+  @JsMethod(name = "getAtIndex")
   E get(int index);
 
   int indexOf(Object o);
@@ -62,6 +63,7 @@
     }
   }
 
+  @JsMethod(name = "setAtIndex")
   E set(int index, E element);
 
   @JsIgnore