[DebugInfo] Add a new method IPDBSession::findLineNumbersBySectOffset

Summary:
Some PDB symbols do not have a valid VA or RVA but have Addr by Section and Offset. For example, a variable in thread-local storage has the following properties:

     get_addressOffset: 0
     get_addressSection: 5
     get_lexicalParentId: 2
     get_name: g_tls
     get_symIndexId: 12
     get_typeId: 4
     get_dataKind: 6
     get_symTag: 7
     get_locationType: 2

This change provides a new method to locate line numbers by Section and Offset from those symbols.

Reviewers: zturner, rnk, llvm-commits

Subscribers: asmith, JDevlieghere

Differential Revision: https://reviews.llvm.org/D44407

llvm-svn: 327601