Support non-public anno. attr. values in AnnoUtils

Prior to this commit, the getValue(Annotation, String) method in
AnnotationUtils failed to retrieve the value of the desired annotation
attribute if the annotation itself was not public -- for example if the
annotation was declared as package private.

This commit addresses this issue by ensuring that getValue(Annotation,
String) uses reflection to make the desired annotation attribute method
accessible before attempting to invoke it to retrieve the value.

Issue: SPR-11104