Debug info: Fixed faulty debug locations for attributed statements

Summary:
As the attributed statements are considered simple statements no
stoppoint was generated before emitting attributed do/while/for/range-
statement. This lead to faulty debug locations.

Reviewers: echristo, aaron.ballman, dblaikie

Reviewed By: dblaikie

Subscribers: bjope, aprantl, cfe-commits

Differential Revision: https://reviews.llvm.org/D37428

llvm-svn: 312623