Document composed support for @Scheduled, @JmsListener, & @Sql

Issue: SPR-13973

spring-context/src/main/java/org/springframework/scheduling/annotation/Scheduled.java

@@ -36,6 +36,9 @@ import java.lang.annotation.Target;
  * done manually or, more conveniently, through the {@code <task:annotation-driven/>}
  * element or @{@link EnableScheduling} annotation.
  *
+ * <p>This annotation may be used as a <em>meta-annotation</em> to create custom
+ * <em>composed annotations</em> with attribute overrides.
+ *
  * @author Mark Fisher
  * @author Dave Syer
  * @author Chris Beams

spring-context/src/main/java/org/springframework/scheduling/annotation/Schedules.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 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.
@@ -30,6 +30,9 @@ import java.lang.annotation.Target;
  * where {@link Scheduled} can simply be declared several times on the same method,
  * implicitly generating this container annotation.
  *
+ * <p>This annotation may be used as a <em>meta-annotation</em> to create custom
+ * <em>composed annotations</em>.
+ *
  * @author Juergen Hoeller
  * @since 4.0
  * @see Scheduled