Add @FunctionalInterface on candidate interfaces

Issue: SPR-14432

spring-aop/src/main/java/org/aopalliance/intercept/MethodInterceptor.java

@@ -39,6 +39,7 @@ package org.aopalliance.intercept;
  *
  * @author Rod Johnson
  */
+@FunctionalInterface
 public interface MethodInterceptor extends Interceptor {
 	
 	/**

spring-aop/src/main/java/org/springframework/aop/ClassFilter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2007 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -27,6 +27,7 @@ package org.springframework.aop;
  * @see Pointcut
  * @see MethodMatcher
  */
+@FunctionalInterface
 public interface ClassFilter {
 
 	/**

spring-aop/src/main/java/org/springframework/aop/framework/autoproxy/TargetSourceCreator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -29,6 +29,7 @@ import org.springframework.aop.TargetSource;
  * @author Rod Johnson
  * @author Juergen Hoeller
  */
+@FunctionalInterface
 public interface TargetSourceCreator {
 
 	/**

spring-aop/src/main/java/org/springframework/aop/interceptor/AsyncUncaughtExceptionHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -29,6 +29,7 @@ import java.lang.reflect.Method;
  * @author Stephane Nicoll
  * @since 4.1
  */
+@FunctionalInterface
 public interface AsyncUncaughtExceptionHandler {
 
 	/**