Put PDB parsing code into a pdb namespace.

llvm-svn: 268072
diff --git a/llvm/lib/DebugInfo/PDB/Raw/RawSession.cpp b/llvm/lib/DebugInfo/PDB/Raw/RawSession.cpp
index dcdbcb4..330e439 100644
--- a/llvm/lib/DebugInfo/PDB/Raw/RawSession.cpp
+++ b/llvm/lib/DebugInfo/PDB/Raw/RawSession.cpp
@@ -18,6 +18,7 @@
 #include "llvm/Support/MemoryBuffer.h"
 
 using namespace llvm;
+using namespace llvm::pdb;
 
 RawSession::RawSession(std::unique_ptr<PDBFile> PdbFile)
     : Pdb(std::move(PdbFile)) {}