[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
diff --git a/llvm/unittests/DebugInfo/PDB/PDBApiTest.cpp b/llvm/unittests/DebugInfo/PDB/PDBApiTest.cpp
index 4cc47aa..2b8050a 100644
--- a/llvm/unittests/DebugInfo/PDB/PDBApiTest.cpp
+++ b/llvm/unittests/DebugInfo/PDB/PDBApiTest.cpp
@@ -88,6 +88,11 @@
   findLineNumbersByAddress(uint64_t Address, uint32_t Length) const override {
     return nullptr;
   }
+  std::unique_ptr<IPDBEnumLineNumbers>
+  findLineNumbersBySectOffset(uint32_t Section, uint32_t Offset,
+                              uint32_t Length) const override {
+    return nullptr;
+  }
   std::unique_ptr<IPDBEnumSourceFiles>
   findSourceFiles(const PDBSymbolCompiland *Compiland, llvm::StringRef Pattern,
                   PDB_NameSearchFlags Flags) const override {