[DebugInfo] Combine Trivial and NonTrivial flags

Summary:
Companion to https://reviews.llvm.org/D59347


Reviewers: rnk, zturner, probinson, dblaikie, deadalnix

Subscribers: aprantl, jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59348

llvm-svn: 358220