Fixes spelling in comments and removes compile time warnings

JSONStringer.java

@@ -72,6 +72,7 @@ public class JSONStringer extends JSONWriter {
      * <code>endArray</code>).
      * @return The JSON text.
      */
+    @Override
     public String toString() {
         return this.mode == 'd' ? this.writer.toString() : null;
     }