* pull424:
  typo in pointcut expression

Issue: SPR-11584

This commit validates that the payload type of the message is
assignable to the one declared in the method signature. If that
is not the case, a meaningful exception message is thrown with
the types mismatch.

Prior to this commit, only the Message interface could be defined
in the method signature: it is now possible to define a sub-class
of Message if necessary which will match as long as the Message
parameter is assignable to that type.

Issue: SPR-11584

Issue: SPR-11578

Issue: SPR-11239

Issue: SPR-11575

This change updates the XML namespace to match a change already made
to the Java config.

Issue: SPR-11578

Issue: SPR-11527

Issue: SPR-11527

Issue: SPR-11527

BufferingStompDecoder message buffer size limit can now be configured
with JavaConfig MessageBrokerRegistry.setMessageBufferSizeLimit() or
with XML <websocket:message-brocker message-buffer-size="">.

Issue: SPR-11527

Before this change the StompDecoder decoded and returned only the first
Message in the ByteBuffer passed to it. So to obtain all messages from
the buffer, one had to loop passing the same buffer in until no more
complete STOMP frames could be decoded.

This chage modifies StompDecoder to return List<Message> after
exhaustively decoding all available STOMP frames from the input buffer.
Also an overloaded decode method allows passing in Map that will be
populated with any headers successfully parsed, which is useful for
"peeking" at the "content-length" header.

This change also adds a BufferingStompDecoder sub-class which buffers
any content left in the input buffer after parsing one or more STOMP
frames. This sub-class can also deal with fragmented messages,
re-assembling them and parsing as a whole message.

Issue: SPR-11527

Issue: SPR-11591

Revised ResizableByteArrayOutputStream as an actual subclass of ByteArrayOutputStream, and consistently applied appropriate ByteArrayOutputStream initial capacities across the codebase

Issue: SPR-11594

This commit adds new MockHttpServletRequestBuilder constructors
with an URI parameter in addition to the URL template + URL variables
existing ones.

It gives more control on how the URL is built, allowing for example to
use URL variables containing '/' character with proper encoding.

Issue: SPR-11441

Prior to this commit, the ShallowEtagHeaderFilter did not use the
content length given by the content generator to set the
ByteArrayOutputStream's buffer size.
This can lead to performance issues for large content since the buffer
grows as the content is being written.

This commit adds a new ByteArrayOutputStream variant called
ResizableByteArrayOutputStream. This implementation has public methods
for modifying the internal buffer size and does not synchronize on
buffer access.
This commit also make use of this new variant in
ShallowEtagHeaderFilter.

Issue: SPR-8271

Issue: SPR-11574

SessionFlashMapManager also clears the session attribute now when the given FlashMap List is empty.

Issue: SPR-11538

Issue: SPR-11548

Expand SockJS documentation

Issue: SPR-11437

Issue: SPR-11496, SPR-11525

Issue: SPR-11556