Add SubProtocolHandler to encapsulate the logic for using a
sub-protocol.

A SubProtocolWebSocketHandler is also provided to
delegate to the appropriate SubProtocolHandler based on the
negotiated sub-protocol value at handshake.

StompSubProtocolHandler provides handling for STOMP messages.

Issue: SPR-10786

Issue: SPR-10777
(cherry picked from commit 9035a97e)

Issue: SPR-10788
(cherry picked from commit d32a77a5)

Issue: SPR-10800

After this change the top-level sockjs package contains the main types
for use in applications.

A SockJS message frame is an array of JSON-encoded messages and before
this change the use of the Jackson 2 library was hard-coded.

A Jackson 2 and Jackson 1.x implementations are provided and
automatically used if those libraries are present on the classpath.

Issue: SPR-10800

Issue: SPR-10752
Issue: SPR-10627
(cherry picked from commit ae0f23e9)

Issue: SPR-10767
(cherry picked from commit d0948f1f)

PropertySourcesPlaceholderConfigurer's "ignoreUnresolvablePlaceholders" setting reliably applies to nested placeholders as well

Issue: SPR-10549

Issue: SPR-10591

Issue: SPR-10609

Issue: SPR-10509

Issue: SPR-10779

Issue: SPR-10701

Issue: SPR-10775

Issue: SPR-10775

Issue: SPR-10775

Issue: SPR-10558

Issue: SPR-10558

Issue: SPR-10657

Issue: SPR-10663

# By Biju Kunjummen
* SPR-10714:
  Fix Jaxb2TypeScanner to scan for @XmlRegistry

Update ClassPathJaxb2TypeScanner to scan for @XmlRegistry classes.

Prior to this commit explicitly configured @XmlRegistry annotated classes
were not registered with the JAXBContext when using the 'packagesToScan'
property of the Jaxb2Unmarshaller.

Issue: SPR-10714

It makes it possible to deploy multiple WebSocketHandler's to a URL,
each supporting a different sub-protocol.

Issue: SPR-10786

The method WsServerContainer.getServerContainer() was removed from
JSR-356 but remained in Tomcat a little while longer. Instead the
ServerContainer is obtained through a ServletContext attribute.
Tomcat has now removed this method, hence the need for this fix.

Fix ResourceHttpRequestHandler to only log warning when locations
is empty.

Issue: SPR-10780

Reduce INFO level destroy logging to DEBUG

Issue: SPR-10758

SI's BeanFactoryChannelResolver was BeanFactoryAware. This commit
brings Spring's BeanFactoryMessageChannelDestinationResolver in line
with the old SI class.

Previously the Jibx binding was commented out which caused failures when
using the TestGroup.CUSTOM_COMPILATION

Now the Jibx bindings are enabled when the CUSTOM_COMPILATION is enabled.

Issue: SPR-10558

Previously building with JDK > 1.8 b88 caused test failures due to errors
with custom compilers like Jibx and Jasper reports.

This commit adds a new TestGroup named CUSTOM_COMPILATION that allows the
CI server to continue to run these tests but allow committers to ignore
these tests.

Moved executor null check to AsyncExecutionInterceptor, allowing AbstractAsyncExecutionAspect to fall back to sync execution (as in 3.2.1)

Issue: SPR-10636

Resource-based PlatformTransactionManager implementations defensively catch Throwable in doBegin in order to reliably close resource in case of OutOfMemoryError

Issue: SPR-10755

Issue: SPR-10340