Issue: SPR-12181

Issue: SPR-12182

Per the Javadoc for the SocketUtils() constructor, SocketUtils can be
instantiated as a Spring Bean in XML configuration files; however,
SocketUtils is currently abstract which prevents such usage.

This commit removes the 'abstract' declaration thereby allowing
SocketUtils to be instantiated as a Spring bean.

Issue: SPR-12169

Issue: SPR-11310
Issue: SPR-10548

Prior to this commit, when there was a lot of entries in the
ResolvableType.cache HashMap, getting a simple value could
take a lot of time due to a lot of calls to ResolvableType.equals().
ResolvableType.equals() used this.type, getSource(),
this.variableResolver.getSource() and this.componentType, but
ResolvableType.hashCode() used only this.type.

With this commit, ResolvableType.hashCode() now uses the same
fields than ResolvableType.equals().

Performance on the spring-resolvabletype-benchmark project:
 - 8000 us before this commit
 - 120 us with this commit

Issue: SPR-12122

Revised ResourcePropertySource in order to avoid ConfigurationClassProcessor's AnnotationPropertySource subclass

Issue: SPR-12115

Fix CompositePropertySourceTests which fails when run we debug logging.

Rework the @PropertySource parsing logic recently changed in commit
7c608886 to deal with the same source appearing on a @Configuration
class and an @Import class.

Processing now occurs in a single sweep, with any previously added
sources being converted to a CompositePropertySource.

Issue: SPR-12115

PropertySource implementations perform conversion to String arrays via StringUtils (getting rid of EMPTY_NAMES_ARRAY)

Issue: SPR-12095

Prior to this commit, there was no declarative mechanism for a custom
TestExecutionListener to be registered as a default
TestExecutionListener.

This commit introduces support for discovering default
TestExecutionListener implementations via the SpringFactoriesLoader
mechanism. Specifically, the spring-test module declares all core
default TestExecutionListeners under the
org.springframework.test.context.TestExecutionListener key in its
META-INF/spring.factories properties file, and third-party frameworks
and developers can contribute to the list of default
TestExecutionListeners in the same manner.

 - AbstractTestContextBootstrapper uses the SpringFactoriesLoader to
   look up the class names of all registered default
   TestExecutionListeners and sorts the instantiated listeners using
   AnnotationAwareOrderComparator.

 - DefaultTestContextBootstrapper and WebTestContextBootstrapper now
   rely on the SpringFactoriesLoader mechanism for finding default
   TestExecutionListeners instead of hard coding fully qualified class
   names.

 - To ensure that default TestExecutionListeners are registered in the
   correct order, each can implement Ordered or declare @order.

 - AbstractTestExecutionListener and all default TestExecutionListeners
   provided by Spring now implement Ordered with appropriate values.

 - Introduced "copy constructors" in MergedContextConfiguration and
   WebMergedContextConfiguration

 - SpringFactoriesLoader now uses AnnotationAwareOrderComparator
   instead of OrderComparator.

Issue: SPR-11466

Issue: SPR-12078

Issue: SPR-12065

Replace references to the old RFC 2616 (HTTP 1.1) with references
to the new RFCs 7230 to 7235.

This commit also deprecates:
 - HttpStatus.USE_PROXY
 - HttpStatus.REQUEST_ENTITY_TOO_LARGE in favor of HttpStatus.PAYLOAD_TOO_LARGE
 - HttpStatus.REQUEST_URI_TOO_LONG in favor of HttpStatus.URI_TOO_LONG

Issue: SPR-12067

Prior to this commit, given an enum which implements some interface,
GenericConversionService would select the String -> Enum converter even
if a converter for String -> SomeInterface was registered.  This also
affected converters that were registered for String ->
SomeBaseInterface, when SomeInterface extended SomeBaseInterface.

This change modifies the behavior of the private method
getClassHierarchy() by placing Enum.class as late as possible, pretty
much the same way as Object.class is handled.

Issue: SPR-12050

Issue: SPR-12042

Issue: SPR-12002

Make it possible to use a ListenableFuture with Java 8
lambda expressions, using a syntax like
listenableFuture.addCallback(() -> ..., () -> ...);

Issue: SPR-11820

The StaxStreamXMLReader no longer handles all whitespace as ignorable
whitespace.

Issue: SPR-12000

Issue: SPR-11660

In order to be able to use separators like "." (used by default
by most broker relays) instead of "/" for destination patterns
handling, the PathMatcher used in spring-messaging can now
be customized easily thanks to XML websocket namespace
or JavaConfig.

AntPathMatcher has been updated in order to use the configured path
separator instead of an hardcoded "/" for path concatenation.
Extension handling is now disabled when the "." separator is configured.

Issue: SPR-11660

Issue: SPR-11979

Issue: SPR-11746

Issue: SPR-9616