Reverse SPR-10402 change that caused 3.2.3 regression

SPR-10402 in Spring Framework 3.2.3 treated empty request parameter
values as missing values, if the empty value was turned into a null
by a PropertyEditor or Converter. This caused the regression.

Issue: SPR-10578, SPR-10402, SPR-10584
Add mvc: prefix to mapping samples in ref docs

Add 'mvc:' namespace prefix to 'mapping' and 'exclude-mapping' elements
in the reference documentation.

Issue: SPR-10670
Add HTTP method to RequestDataValueProcessor method

Issue: SPR-10041, SPR-10652
Add accept(String) method to mock request builder

Issue: SPR-10390
Add getResult/hasResult methods to DeferredResult

Issue: SPR-10603
Fix getters to match setters in RMHA

Issue: SPR-10519
Inject @Configuration BeanFactory before autowire

Add EnhancedConfigurationBeanPostProcessor to inject the BeanFactory
into EnhancedConfiguration classes before the
AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues method
is called.

Prior to this commit it was possible for @Autowire in a @Configuration
class to invoke an enhanced configuration class method before the
BeanFactory was injected. This is due to the fact that the
AutowiredAnnotationBeanPostProcessor was called before
AbstractAutowireCapableBeanFactory.invokeAwareMethods().

Issue: SPR-10668
Skip abstract beans in getBeansWithAnnotation()

Update BeanFactory.getBeansWithAnnotation() to skip any abstract
bean definitions.

Issue: SPR-10663
Use 'Integer' not 'int' in queryForObject  docs

Update queryForObject calls in the JDBC reference documentation to
use 'Integer.class' rather than the unsupported 'int.class'.

Issue: SPR-10651