Disable ext entities in SourceHttpMessageConverter

This change disables the processing of external entities in
SourceHttpMessageConverter by default and provides an option to enable
it if required.
Use final keyword in MessageHeaders
Fix exception mock request builder

Issue: SPR-11043
Fold spring-test-mvc sources into spring-test

With spring-test compiling against Servlet 3.0 it is no longer required
to compile Spring MVC Test sources separately (from spring-test).
Poish asciidoctor

Issues: SPR-10960
grate documentation to #	deleted:    src/reference/docbook/index.xml
Poish asciidoctor

Issues: SPR-10960
Return 415 on bad request body content-type

Issue: SPR-10982
Poish asciidoctor

Issues: SPR-10960
JndiObjectFactoryBean converts a "defaultObject" value to the expected type if necessary

Issue: SPR-11039
Added test for placeholder in alias definition

Issue: SPR-11018
Add div around extra hidden fields in FormTag

Issue: SPR-10926
Handle UnsupportedOperationException from getInstalledExtensions in Glassfish 4.0
Use AsciiDoctor special characters

 - Replaced ellipsis with "..."

 - Replaced em dash with "--"

 - Fixed issue with italics migration in the Standard Annotation Support
  section of the Testing chapter
Update user destinations handling

Before this change subscribing to a user-specific destination in STOMP
required manually appending a unique queue suffix provided in a header
with the CONNECTED frame.

This change removes the need to do that. Instead STOMP clients can
subscribe to "/user/queue/error" and can then begin to receive messages
sent to "/user/{username}/queue/error" without colliding with any other
user doing the same.

Issue: SPR-11077
Return AbstractSubscribableChannel from @Bean methods

Declare SubscribableChannel @Beans in
WebSocketMessageBrokerConfigurationSupport as
AbstractSubscribableChannel to avoid the need for casting when
registering interceptors.

Issue: SPR-11065
Simplify determination of SockJS path

The SockJS path is now passed to the SockJsService handleRequest method
thus removing the need to guess it.

Issue: SPR-11058
Fix a typo in package description
Put accidentally deleted LF in place
Merge pull request #408 from AlexYursha/patch-1

Fix a typo in package description