[PDB] Fix section contributions

Summary:
PDB section contributions are supposed to use output section indices and
offsets, not input section indices and offsets.

This allows the debugger to look up the index of the module that it
should look up in the modules stream for symbol information. With this
change, windbg can now find line tables, but it still cannot print local
variables.

Fixes PR34048

Reviewers: zturner

Subscribers: hiraditya, ruiu, llvm-commits

Differential Revision: https://reviews.llvm.org/D36285

llvm-svn: 309987