[PDB] Add a module descriptor for every object file

Summary:
Expose the module descriptor index and fill it in for section
contributions.

Reviewers: zturner

Subscribers: llvm-commits, ruiu, hiraditya

Differential Revision: https://reviews.llvm.org/D34126

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@305296 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed