Fixes a problem when we have multiple inclusion cycles and try to
enumerate all possible ways to reach the max inclusion depth.
rdar://problem/38871876
Reviewers: bruno, rsmith, jkorous, aaron.ballman
Reviewed By: bruno, jkorous, aaron.ballman
Subscribers: dexonsmith, cfe-commits
Differential Revision: https://reviews.llvm.org/D48786
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@337953 91177308-0d34-0410-b5e6-96231b3b80d8