[SourceLocations] Use stronger sort predicate to remove non-deterministic ordering
[SourceLocations] Use stronger sort predicate to remove non-deterministic ordering

Summary:
This fixes the following failure uncovered by D39245:
  Clang :: Index/getcursor-preamble.m

Reviewers: gbenyei, akyrtzi, bkramer, arphaman

Reviewed By: arphaman

Subscribers: arphaman, cfe-commits

Differential Revision: https://reviews.llvm.org/D40618

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@319357 91177308-0d34-0410-b5e6-96231b3b80d8

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