Avoid NPE in AutowiredAnnotationBeanPostProcessor

Prior to this change, AABPP#determineRequiredStatus never checked the
return value of ReflectionUtils#findMethod when searching for a
'#required' attribute. This call returns null for annotations such as
@Inject, @Value and @Resource, and subsequently causes a
NullPointerException to be thrown when ReflectionUtils#invokeMethod is
called. The NPE is caught immediately and #determineRequiredStatus
returns defaulting to true, but this this approach is inefficient. It
is also problematic for users who have set breakpoints on NPE -- they
end up debugging into Spring internals, which is a false positive.

This commit checks the return value of of ReflectionUtils#findMethod,
and in the case of null, eagerly returns true.  There is no change to
external behavior, simply a more efficient and debugging-friendly
implementation.

Existing test cases already cover this change, given that it is purely
a refactoring.

Issue: SPR-9316
Merge pull request #64 from marschall/SPR-9316

* SPR-9316:
  Avoid NPE in AutowiredAnnotationBeanPostProcessor
Optimize memory usage in factory *Metadata classes

InjectionMetadata and LifecycleMetadata can end up having mostly empty
instance variables. In such cases memory usage can be improved a little
bit.

This patch addresses this in two ways:

 - Creating a LinkedHashSet of the "right" size, the default capacity
   is 16 but the exact capacity needed is known in advance.

 - If the argument is empty then use Collections#emptySet which is a
   constant so no additional memory is used. Since it's immutable there
   is no need for the Collections#synchronizedSet wrapper.

Issue: SPR-9264
Merge pull request #37 from marschall/small-memory-fixes

* small-memory-fixes:
  Optimize memory usage in factory *Metadata classes
Cache MethodParameter annotation lookup results

Prior to this change, Spring's MethodParameter#getParameterAnnotations
called java.lang.Method#getParameterAnnotations on every invocation.
The latter ends up contending for a monitor inside (Sun) JDK code. This
is problematic when dealing with the high number of @RequestMapping
invocations that can occur in a Spring MVC @Controller.

This commit eliminates this contention by caching values returned by
java.lang.Method#getParameterAnnotations in a static ConcurrentMap.

Note that only Method parameter annotations are cached, while
Constructor parameter annotations are not. This is because the
issue of primary concern is, as mentioned above, @RequestMapping
methods. By nature, constructors are called much more infrequently, and
in most cases in a single-threaded fashion.

Issue: SPR-9298
Merge pull request #63 from dukehoops/SPR-9298

* SPR-9298:
  Cache MethodParameter annotation lookup results
Pattern suffix issue in AnnotationMethodHandlerAdapter

SPR-9333
Improve documentation for configuration class 'lite' mode

Overhauled the class-level JavaDoc in @Bean:

 - added h3 headers for greater clarity and readability
 - mentioned 'prototype' semantics for lite mode

Issue: SPR-9401
Fix minor grammatical errors in AbstractBeanDefinition
Fix annotation search ending too early

In AnnotationUtils#findAnnotation(Method, Class), the search for a
method annotation fails if:

 - the original method does not have the annotation

 - an abstract superclass does not have an equivalent method declared

 - an interface implemented by the superclass has the method and
   the annotation -> this should be found, but is not!

This happens because the try-catch block in #findAnnotation is too wide:
cl.getDeclaredMethod() can throw NoSuchMethodException and skip the
'#searchOnInterfaces' call prematurely.

The try-catch block was made narrower to allow #searchOnInterfaces to
be called even if the abstract class does not have the method declared
at all.

Issue: SPR-9342
Merge pull request #81 from JanecekPetr/SPR-9342

* SPR-9342:
  Fix annotation search ending too early
Improve documentation of @Bean 'lite' mode

Updated the class-level JavaDoc for @Bean to better explain the
semantics of 'lite' mode.

Renamed "Configuration Class Lite Mode" to "@Bean Lite Mode".

Added discussion of @DependsOn to the class-level JavaDoc.

Issue: SPR-9401
Improve documentation of @Bean 'lite' mode

Removed misleading mention of "configuration classes" in the
"@Bean Lite Mode" section.

Issue: SPR-9401