[analyzer] Use recursive AST visitor to drive simple visitation order in

[analyzer] Use recursive AST visitor to drive simple visitation order in
AnalysisConsumer.

As a result:
 - We now analyze the C++ methods which are defined within the
class body. These were completely skipped before.

- Ensure that AST checkers are called on functions in the
order they are defined in the Translation unit.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152650 91177308-0d34-0410-b5e6-96231b3b80d8