Fix several miscellaneous compiler/Eclipse warnings

- Suppress an (intentional) AspectJ warning
 - Remove unused imports
 - Suppress a [hiding] warning
 - Fix a generics warning related to extension of final types

Issue: SPR-9431

spring-aspects/src/test/java/org/springframework/aop/aspectj/autoproxy/CodeStyleAspect.aj

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.aop.aspectj.autoproxy;
 
+import org.aspectj.lang.annotation.SuppressAjWarnings;
+
 /**
  * @author Adrian Colyer
  */
@@ -25,6 +27,7 @@ public aspect CodeStyleAspect {
 
 	pointcut somePC() : call(* someMethod());
 
+	@SuppressAjWarnings("adviceDidNotMatch")
 	before() : somePC() {
 		System.out.println("match");
 	}