[codeview] respect signedness of APSInts when printing to YAML

[inglorion]

Summary

This fixes a bug where we always treat APSInts in Codeview as
signed when writing them to YAML. One symptom of this problem is that
llvm-pdbdump raw would show Enumerator Values that differ between the
original PDB and a PDB that has been round-tripped through YAML.

[zturner]

I thought I lgtm'ed this already. Maybe I did it through email and it didn't show up? Anyway, sorry, lgtm

llvm/trunk/lib/ObjectYAML/CodeViewYAMLTypes.cpp

StringRef ScalarTraits<TypeIndex>::input(StringRef Scalar, void *Ctx,
   uint32_t I;
   StringRef Result = ScalarTraits<uint32_t>::input(Scalar, Ctx, I);
   S.setIndex(I);
   return Result;
 }
 
 void ScalarTraits<APSInt>::output(const APSInt &S, void *,
                                   llvm::raw_ostream &OS) {
-  S.print(OS, true);
+  S.print(OS, S.isSigned());
 }
 
 StringRef ScalarTraits<APSInt>::input(StringRef Scalar, void *Ctx, APSInt &S) {
   S = APSInt(Scalar);
   return "";
 }
 
 void ScalarEnumerationTraits<TypeLeafKind>::enumeration(IO &io,

llvm/trunk/test/DebugInfo/PDB/pdbdump-yaml-types.test

 YAML:         - Kind:            LF_ENUMERATE
 YAML:           Enumerator:      
 YAML:             Attrs:           3
 YAML:             Value:           16384
 YAML:             Name:            eIDLModuleUsage
 YAML:         - Kind:            LF_ENUMERATE
 YAML:           Enumerator:      
 YAML:             Attrs:           3
-YAML:             Value:           -32768
+YAML:             Value:           32768
 YAML:             Name:            eAnonymousUsage
 YAML:         - Kind:            LF_ENUMERATE
 YAML:           Enumerator:      
 YAML:             Attrs:           3
 YAML:             Value:           65536
 YAML:             Name:            eTypedefUsage
 YAML:         - Kind:            LF_ENUMERATE
 YAML:           Enumerator: