Fix llvm-pdbutil to handle new built-in types

[amccarth]

Summary

The built-in PDB types enum has been extended to include char16_t and char32_t.
llvm-pdbutil was hitting an llvm_unreachable because it didn't know about these
new values. The new values are not yet in the DIA documentation, but are
listed in the cvconst.h header that comes as part of the DIA SDK.

llvm/trunk/include/llvm/DebugInfo/PDB/PDBTypes.h

enum class PDB_BuiltinType {
   Long = 13,
   ULong = 14,
   Currency = 25,
   Date = 26,
   Variant = 27,
   Complex = 28,
   Bitfield = 29,
   BSTR = 30,
-  HResult = 31
+  HResult = 31,
+  Char16 = 32,
+  Char32 = 33
 };
 
 /// These values correspond to the flags that can be combined to control the
 /// return of an undecorated name for a C++ decorated name, and are documented
 /// here: https://msdn.microsoft.com/en-us/library/kszfk0fs.aspx
 enum PDB_UndnameFlags: uint32_t {
   Undname_Complete = 0x0,
   Undname_NoLeadingUnderscores = 0x1,

llvm/trunk/tools/llvm-pdbutil/PrettyBuiltinDumper.cpp

StringRef BuiltinDumper::getTypeName(const PDBSymbolTypeBuiltin &Symbol) {
   case PDB_BuiltinType::Bitfield:
     return "bitfield";
   case PDB_BuiltinType::BSTR:
     return "BSTR";
   case PDB_BuiltinType::HResult:
     return "HRESULT";
   case PDB_BuiltinType::BCD:
     return "HRESULT";
+  case PDB_BuiltinType::Char16:
+    return "char16_t";
+  case PDB_BuiltinType::Char32:
+    return "char32_t";
   case PDB_BuiltinType::None:
     return "...";
   }
   llvm_unreachable("Unknown PDB_BuiltinType");
 }