report generator should merge annotated listings for inner classes

When the report generator generates the annotated listing for a source file,
it generates a listing for each *class*, not each *source file*.

It would be more intuitive to look at a source file and see all the
coverage data in it, whether in the main class or in inner classes.

If the current behavior is deemed important enough to keep, it would be
good to provide an option for this alternate nbehaior, so it is selectable
by the end user.