[AutoComplete] Use stronger sort predicate for autocomplete candidates to...

[AutoComplete] Use stronger sort predicate for autocomplete candidates to remove non-deterministic ordering

Summary: This fixes the failure in test/Driver/autocomplete.c uncovered by D39245.

Reviewers: yamaguchi, teemperor, ruiu

Reviewed By: yamaguchi, ruiu

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D40234

llvm-svn: 318681