Add proper callbacks for DeclStmt -- we weren't recursing on

        the decls.  This was just an oversight before; one we didn't
        catch because lots of information in a DeclStmt was also being
        traversed (redundantly) elsewhere.

        Once DeclStmt was cleaned up, I could clean up some of the
        redundant traversals found elswhere as well -- in particular,
        traversing the declarations inside a function as part of the
        function callback (instead of as part of the CompoundExpr
        callback that constitutes the body of the function).  The old
        way was really weird, and led to some parts of local variable
        declarations (but not all) being visited twice.  That is now
        resolved.  I also was able to simplify the traversers for
        IfStmt/WhileStmt/etc, which used to have redundant calls to
        work around the fact DeclStmt wasn't working properly.

        While in the area, I fixed up a few more recursion-ordering
        issues.  I try to hold to the principle that
        RecursiveASTVisitor visits objects in the source code in the
        same order they're typed.  So the return-type of a variable
        comes before the variable-name.  This still isn't perfect, but
        we're closer to that.

	Reviewed by chandlerc and wan.

llvm-svn: 109590