Fix transitive dependency issue with slf4j-api

Before this change, IDE settings generated via import-into-eclipse.sh
created a classpath dependency on slf4j-api version 1.6.1 and
slf4j-log4j12 version 1.5.10. As a result running tests inside the IDE
resulted in a NoSuchMethodException.

build.gradle sets the variable slf4jLog4jVersion to '1.5.10'. However,
the hibernate-validator dependency in spring-context pulls in
slf4j-api version 1.6.1. The change ensures the version specified in
the build script variable is used consistently. Whether it should be
1.5.10 or 1.6.1 is a separate concern.
Merge pull request #61 from rstoyanchev/slf4j-dependency

* rstoyanchev/slf4j-dependency:
  Fix transitive dependency issue with slf4j-api
Upgrade slf4j-api and -log4j12 dependencies to 1.6.1

Previously depending on 1.5.10 in certain locations, which caused
NoClassDefFoundErrors in EhCacheCacheTests and other tests due to
mismatches between slf4j -api and -log4j12 versions.

With the exception of one transitive dependency via Hibernate 3.3.1.GA,
all slf4j dependencies are now pegged at 1.6.1 (and all tests pass).
Initial cut of Servlet 3.0 based async support

From a programming model perspective, @RequestMapping methods now
support two new return value types:

* java.util.concurrent.Callable - used by Spring MVC to obtain the
return value asynchronously in a separate thread managed transparently
by Spring MVC on behalf of the application.
* org.springframework.web.context.request.async.DeferredResult - used
by the application to produce the return value asynchronously in a
separate thread of its own choosing.

The high-level idea is that whatever value a controller normally
returns, it can now provide it asynchronously, through a Callable or
through a DeferredResult, with all remaining processing --
@ResponseBody, view resolution, etc, working just the same but
completed outside the main request thread.

From an SPI perspective, there are several new types:

* AsyncExecutionChain - the central class for managing async request
processing through a sequence of Callable instances each representing
work required to complete request processing asynchronously.
* AsyncWebRequest - provides methods for starting, completing, and
configuring async request processing.
* StandardServletAsyncWebRequest - Servlet 3 based implementation.
* AsyncExecutionChainRunnable - the Runnable used for async request
execution.

All spring-web and spring-webmvc Filter implementations have been
updated to participate in async request execution.
The open-session-in-view Filter and interceptors implementations in
spring-orm will be updated in a separate pull request.

Issue: SPR-8517
Fix broken test

Issue: SPR-8517
Upgrade to docbook-reference-plugin 0.1.5

 - Fixes deprecation warnings associated with recent upgrade to Gradle
   1.0-rc1
Polish Servlet async request processing

* Clarify semantics and behavior of AsyncWebRequest methods in most cases
making a best effort and not raising an exception if async processing
has completed for example due to a timeout. The startAsync() method is
still protected with various checks and will raise ISE under a number
of conditions.
* Return 503 (service unavailable) when requests time out.
* Logging improvements.

Issue: SPR-8517
Add ability to handle a timeout to DeferredResult

When a controller returns a DeferredResult, the underlying async
request will eventually time out. Until now the default behavior was
to send a 503 (SERVICE_UNAVAILABLE). However, this is not desirable
in all cases. For example if waiting on an event, a timeout simply
means there is no new information to send.

To handle those cases a DeferredResult now accespts a timeout result
Object in its constructor. If the timeout occurs before the
DeferredResult is set, the timeout result provided to the constructor
is used instead.

Issue: SPR-8617
Fix encoding issues in javadoc

Before this change javadoc in two classes had non-UTF-8 encoded
characters. This caused building Spring API to fail in Java 1.7.

Commit fixes this by replacing wrongly encoded characters with their
UTF-8 equivalents.

Issue: SPR-9097
Merge pull request #35 from sslavic/SPR-9097

* SPR-9097:
  Fix encoding issues in javadoc
Fix javadoc warnings

Before this change there were numerous javadoc warnings being reported
while building Spring framework API.

This commit resolves most of the javadoc warnings, reducing the total
number from 265 to 103.

Issue: SPR-9113
Merge pull request #36 from sslavic/SPR-9113

* SPR-9113:
  Fix javadoc warnings
Convert SpEL plus operands using reg'd converters

Prior to this commit, SpEL's OpPlus ('+' operator) would convert its
left and right operands to String directly via #toString calls.

This change ensures that operand values are delegated to any registered
converters, allowing for customization of the stringified output.

Note that the OpPlus constructor now throws IllegalArgumentException if
zero operands are supplied.

Issue: SPR-8308
Merge pull request #7 from bedla/SPR-8308

* SPR-8308:
  Convert SpEL plus operands using reg'd converters
Fix scoped-proxy memory leak w/ @Resource injection

Prior to this change, request-scoped components having
@Resource-injected dependencies caused a memory leak in
DefaultListableBeanFactory#dependenciesForBeanMap.

Consider the following example:

    @Component
    @Scope(value="request", proxyMode=ScopedProxyMode.TARGET_CLASS)
    public class MyComponent {

        @Resource
        private HttpServletRequest request;

        // ...
    }

The bean name for "MyComponent" will end up being
'scopedTarget.myComponent', which will become a key in
the #dependenciesForBeanMap structure.

On the first request, the injected HttpServletRequest bean will be a
proxy and will internally have a bean name of the form
"$Proxy10@1a3a2a52". This name will be added to the Set value associated
with the 'scopedTarget.myComponent' entry in #dependenciesForBeanMap.

On the second request, the process will repeat, but the injected
HttpServletRequest will be a different proxy instance, thus having a
different identity hex string, e.g. "$Proxy10@5eba06ff". This name will
also be added to the Set value associated with the
'scopedTarget.myComponent' entry in #dependenciesForBeanMap, and this
is the source of the leak: a new entry is added to the set on each
request but should be added only once.

This commit fixes the leak by introducing caching to
CommonAnnotationBeanPostProcessor#ResourceElement similar to that already
present in AutowiredAnnotationBeanPostProcessor#AutowiredFieldElement
and #AutowiredMethodElement. Essentially, each ResourceElement instance
now tracks whether it has been created, caches the ultimate value to be
injected and returns it eagerly if necessary. Besides solving the memory
leak, this has the side effect of avoiding unnecessary proxy creation.

This fix also explains clearly why injection into request-scoped
components using @Autowired never suffered this memory leak: because the
correct caching was already in place. Because @Resource is considerably
less-frequently used than @Autowired, and given that this particular
injection arrangement is relatively infrequent, it becomes
understandable how this bug has been present without being reported
since the introduction of @Resource support in Spring 2.5: developers
were unlikely to encounter it in the first place; and if they did, the
leak was minor enough (adding strings to a Set), that it could
potentially go unnoticed indefinitely depending on request volumes and
available memory.

Issue: SPR-9176
Merge pull request #66 from dridi/SPR-9176

* SPR-9176:
  Fix scoped-proxy memory leak w/ @Resource injection
Fix issue with encoded params in UriComponentsBuilder

The fromUri method of UriComponentsBuilder used uri.getXxx() methods,
which decode the URI parts causing URI parsing issues. The same method
now uses uri.getRawXxx().

Issue: SPR-9317
Javadoc update

Issue: SPR-9265
Add empty location check to ResourceHttpRequestHandler

ResourceHttpRequestHandler now implements InitializingBean and
checks for empty locations.

Issue: SPR-9186
HanderInterceptor and OSIV async request changes

This change updates Open-Session-in-View filters and interceptors for
use in async requests mainly ensuring the open Hibernate session is
unbound from the main request processing thread and bound to the to
async thread.

Issue: SPR-8517