Issue: SPR-13007

* SPR-13007:
  Avoid eager formatting in pre-condition checks

In general, the Spring Framework aims to construct error message
strings only if an actual error has occurred. This seems to be the
common pattern in the codebase and saves both CPU and memory. However,
there are some places where eager error message formatting occurs
unnecessarily.

This commit addresses this issue in the following classes:
AdviceModeImportSelector, AnnotationAttributes, and
ReadOnlySystemAttributesMap.

The change in ReadOnlySystemAttributesMap also avoids a potential
NullPointerException.

Issue: SPR-13007

Issue: SPR-13005

This commit introduces support in the spring-test module for obtaining a
reference to the underlying target object hidden behind one or more
proxies.

Specifically this commit introduces AopTestUtils with two methods:

 - getTargetObject(Object)

 - getUltimateTargetObject(Object)

Issue: SPR-13005

Issue: SPR-11694

Issue: SPR-11694

Issue: SPR-11694

Issue: SPR-12998

Modify to use the ConfigurableApplicationContext in reference document

Issue: SPR-13000

This commit also completes 4.2 schema variants in spring-context.

Issue: SPR-5215

Commit 5648fbfc introduced a
compile-time dependency on spring-beans-groovy in the spring-context
module which breaks the build on the CI server since the Animal Sniffer
task cannot find a JAR file for spring-beans-groovy.

This commit reverts that change so that the "sniffer" task once again
succeeds.

Prior to this commit, the `getAnnotation()` method in `TypeDescriptor`
only supported a single level of meta-annotations. In other words, the
annotation hierarchy would not be exhaustively searched.

This commit provides support for arbitrary levels of meta-annotations
in `TypeDescriptor` by delegating to `AnnotationUtils.findAnnotation()`
within `TypeDescriptor.getAnnotation()`.

Issue: SPR-12793

Issue: SPR-12998

* SPR-12975:
  Remove duplicate separators when combining paths

Prior to this commit, AntPathMatcher would not correctly combine a path
that ends with a separator with a path that starts with a separator.
For example, `/foo/` + `/bar` combined into `/foo//bar`.

Specifically, this commit:

 - Removes the duplicated separator in combined paths

 - Improves RequestMappingInfo's toString() representation

 - Fixes Javadoc formatting in AntPathMatcher

 - Polishes AntPathMatcherTests

 - Polishes Javadoc in AbstractRequestCondition

Issue: SPR-12975

Latest dependency updates (EhCache 2.10, Jackson 2.5.3, JasperReports 6.0.4, SLF4J 1.7.12, Tomcat 8.0.22, Undertow 1.2.5)

Issue: SPR-11807

This commit introduces a messaging.converter.MessageConverter that
marshals to/from XML using the abstractions provided in the OXM module.

Issue: SPR-12726

Issue: SPR-12617

Issue: SPR-12003

Issue: SPR-12009

Issue: SPR-12971

Issue: SPR-12957

Issue: SPR-12983

Issue: SPR-12994

Previous docbook-reference-plugin version used some conflicting
API with Gradle 2.4.

Issue: SPR-12772