Eliminate all Javadoc warnings

- Support external Javadoc links using Gradle's javadoc.options.links

 - Fix all other Javadoc warnings, such as typos, references to
   non-existent (or no longer existent) types and members, etc,
   including changes related to the Quartz 2.0 upgrade (SPR-8275) and
   adding the HTTP PATCH method (SPR-7985).

 - Suppress all output for project-level `javadoc` tasks in order to
   hide false-negative warnings about cross-module @see and @link
   references (e.g. spring-core having a @see reference to spring-web).
   Use the `--info` (-i) flag to gradle at any time to see project-level
   javadoc warnings without running the entire `api` task. e.g.
   `gradle :spring-core:javadoc -i`

 - Favor root project level `api` task for detection of legitimate
   Javadoc warnings. There are now zero Javadoc warnings across the
   entirety of spring-framework. Goal: keep it that way.

 - Remove all @link and @see references to types and members that exist
   only in Servlet <= 2.5 and Hibernate <= 4.0, favoring 3.0+ and 4.0+
   respectively. This is necessary because only one version of each of
   these dependencies can be present on the global `api` javadoc task's
   classpath. To that end, the `api` task classpath has now been
   customized to ensure that the Servlet 3 API and Hibernate Core 4 jars
   have precedence.

 - SPR-8896 replaced our dependency on aspectjrt with a dependency on
   aspectjweaver, which is fine from a POM point of view, but causes
   a spurious warning to be emitted from the ant iajc task that it
   "cannot find aspectjrt on the classpath" - even though aspectjweaver
   is perfectly sufficient. In the name of keeping the console quiet, a
   new `rt` configuration has been added, and aspectjrt added as a
   dependency to it. In turn, configurations.rt.asPath is appended to
   the iajc classpath during both compileJava and compileTestJava for
   spring-aspects.

Issue: SPR-10078, SPR-8275, SPR-7985, SPR-8896

spring-aop/src/main/java/org/springframework/aop/aspectj/annotation/AspectJProxyFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2012 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.
@@ -114,7 +114,7 @@ public class AspectJProxyFactory extends ProxyCreatorSupport {
 	/**
 	 * Add all {@link Advisor Advisors} from the supplied {@link MetadataAwareAspectInstanceFactory}
 	 * to the current chain. Exposes any special purpose {@link Advisor Advisors} if needed.
-	 * @see #makeAdvisorChainAspectJCapableIfNecessary()
+	 * @see AspectJProxyUtils#makeAdvisorChainAspectJCapableIfNecessary(List)
 	 */
 	private void addAdvisorsFromAspectInstanceFactory(MetadataAwareAspectInstanceFactory instanceFactory) {
 		List<Advisor> advisors = this.aspectFactory.getAdvisors(instanceFactory);

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

@@ -33,7 +33,7 @@ import org.springframework.util.StringUtils;
 /**
  * Base class for asynchronous method execution aspects, such as
  * {@link org.springframework.scheduling.annotation.AnnotationAsyncExecutionInterceptor}
- * or {@link org.springframework.scheduling.aspectj.AnnotationAsyncExecutionAspect}.
+ * or {@code org.springframework.scheduling.aspectj.AnnotationAsyncExecutionAspect}.
  *
  * <p>Provides support for <i>executor qualification</i> on a method-by-method basis.
  * {@code AsyncExecutionAspectSupport} objects must be constructed with a default {@code
@@ -87,7 +87,7 @@ public abstract class AsyncExecutionAspectSupport implements BeanFactoryAware {
 
 	/**
 	 * Determine the specific executor to use when executing the given method.
-	 * @returns the executor to use (never {@code null})
+	 * @return the executor to use (never {@code null})
 	 */
 	protected AsyncTaskExecutor determineAsyncExecutor(Method method) {
 		if (!this.executors.containsKey(method)) {