[llvm-pdbdump] Rewrite dumper using visitor pattern.

This increases the flexibility of how to dump different
symbol types -- necessary for context-sensitive formatting of
symbol types -- and also improves the modularity by allowing
the dumping to be implemented in the actual dumper, as opposed
to in the PDB library.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230184 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/DebugInfo/PDB/PDBSymbol.h

@@ -53,7 +53,8 @@ public:
   /// call dump() on the underlying RawSymbol, which allows us to discover
   /// unknown properties, but individual implementations of PDBSymbol may
   /// override the behavior to only dump known fields.
-  virtual void dump(raw_ostream &OS, int Indent, PDB_DumpLevel Level, PDB_DumpFlags Flags) const = 0;
+  virtual void dump(raw_ostream &OS, int Indent,
+                    PDBSymDumper &Dumper) const = 0;
   void defaultDump(raw_ostream &OS, int Indent, PDB_DumpLevel Level) const;
 
   PDB_SymType getSymTag() const;
@@ -83,6 +84,8 @@ public:
   const IPDBRawSymbol &getRawSymbol() const { return *RawSymbol; }
   IPDBRawSymbol &getRawSymbol() { return *RawSymbol; }
 
+  const IPDBSession &getSession() const { return Session; }
+
 protected:
   std::unique_ptr<IPDBEnumSymbols> getChildStats(TagStats &Stats) const;