Refactor the uninitialized field visitor.  Also moved the calls to the visitor
later in the code so that the expressions will have addition processing first.
This catches a few additional cases of uninitialized uses of class fields.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190657 91177308-0d34-0410-b5e6-96231b3b80d8