Improvement in AntPathMatcher.combine method

Issues: SPR-7970
Fix bug with custom RequestCondition

A custom RequestCondition which can be provided by overriding methods
in RequestMappingHandlerMapping worked only for conditions that match
and did not return null (as it should have) for conditions that don't
match.

Issues: SPR-9134
Fix race condition in AnntationMethodHER

Issues: SPR-9138
Fix issue with parsing media types

Invalid Content-Type or Accept header values previously resulted in the
IllegalArgumentException getting propagated. After this change such
errors are detected and generally treated as a "no match", which
may for example result in a 406 in the case of the Accept header.

Issue: SPR-9148
Make 'Content-Disposition' header case insensitive

Previously 'Content-Disposition' was passed to Part.getHeader(String).
However the Javadoc for that method specifies the header should be
case insensitive. Note that the JavaDoc in tomcat-servlet-api doesn't
mention this. It can only be found in the official api JavaDoc:

http://download.oracle.com/otndocs/jcp/servlet-3.0-fr-oth-JSpec/

Issue: SPR-9149
Minor improvement in ExceptionHandlerExceptionResolver

Moved a null check inside a protected method to give protected method
a chance to override what happens in that case.

Issues: SPR-9193
Use the type of the actual return value in @MVC

The new @MVC support classes select a HandlerMethodArgumentResolver
and a HandlerMethodReturnValueHandler statically, i.e. based on
the signature of the method, which means that a controller method
can't declare a more general return type like Object but actually
return a more specific one, e.g.  String vs RedirectView, and
expect the right handler to be used.

The fix ensures that a HandlerMethodReturnValueHandler is selected
based on the actual return value type, which is something that was
supported with the old @MVC support classes. One consequence
of the change is the selected HandlerMethodReturnValueHandler can
no longer be cached but that matches the behavior of the old
@MVC support classes.

Issues: SPR-9218
Fix typo in reference documentation

Issue: SPR-9321
Upgrade to Gradle 1.0-rc1

 - Fix deprecation warnings about dynamic properties; favor use of
   "extra properties extensions" per [1]

 - Certain such deprecations are still issued due to violations within
   the docbook-reference plugin. These will be fixed in an upcoming
   revision of the plugin, at which point spring-framework will upgrade
   to depend on it and these warnings will be eliminated

[1] http://gradle.org/docs/current/dsl/org.gradle.api.plugins.ExtraPropertiesExtension.html

Issue: SPR-9327
Upgrade AspectJ from 1.6.8 to 1.6.12

 - Spring remains compatible against AJ version 1.6.8, but is now
   compiling and testing against 1.6.12

 - Encountered what appears to be an AJ bug introduced in 1.6.10: an
   assertion in org.aspectj.weaver.UnresolvedType causes a false
   negative failure when encountering org.springframework.io.Resource
   arrays, e.g. "[org.springframework.io.Resource@xxx". This problem
   has been reported to the AJ team and in the meantime, the recommended
   workaround is to disable assertions either completely, or at least
   selectively with

       -disableassertions:org.aspectj.weaver.UnresolvedType

Issue: SPR-7989, SPR-9272
Fix typo in ApplicationContext reference doc