Display name of identifier tokens in Visual Studio native visualizer

[mspertus]

Summary

The Token visualizer in clang.natvis makes debugging Clang in Visual Studio much easier for keywords (because a given keyword is always the same), but it doesn't work very well for identifiers (because they are all different). This change has the visualizer display the name of the identifier. I have been using this daily, and I find this simple change has lead to a much-improved day-to-day experience.

[aaron.ballman]

LGTM, thank for you this (I think it's going to help me out quite a bit)!

[mspertus]

Thanks, Aaron! Hal mentioned that I might need to ask you to commit on my behalf as I don't have commit access as of now.

[aaron.ballman]

I've commit in r247442, thank you for the patch!

utils/clang.natvis

<Type Name="clang::DeclarationName">
     <Expand>
       <Item Condition="(Ptr &amp; PtrMask) == StoredIdentifier" Name="[Identifier]">*(clang::IdentifierInfo *)(Ptr &amp; ~PtrMask)</Item>
       <Item Condition="(Ptr &amp; PtrMask) == StoredObjCZeroArgSelector" Name="[ObjC Zero Arg Selector]">*(clang::IdentifierInfo *)(Ptr &amp; ~PtrMask)</Item>
       <Item Condition="(Ptr &amp; PtrMask) == StoredObjCOneArgSelector" Name="[ObjC One Arg Selector]">*(clang::IdentifierInfo *)(Ptr &amp; ~PtrMask)</Item>
       <Item Condition="(Ptr &amp; PtrMask) == StoredDeclarationNameExtra" Name="[Extra]">(clang::DeclarationNameExtra::ExtraKind)((clang::DeclarationNameExtra *)(Ptr &amp; ~PtrMask))-&gt;ExtraKindOrNumArgs</Item>
     </Expand>
   </Type>
   <Type Name="clang::Token">
-    <DisplayString>{(clang::tok::TokenKind)Kind}</DisplayString>
+    <DisplayString Condition="Kind != clang::tok::identifier">{(clang::tok::TokenKind)Kind}</DisplayString>
+    <DisplayString Condition="Kind == clang::tok::identifier">{{Identifier ({*(clang::IdentifierInfo *)(PtrData)})}}</DisplayString>
   </Type>
   <Type Name="clang::DeclSpec">
     <DisplayString>[{(clang::DeclSpec::SCS)StorageClassSpec}], [{(clang::TypeSpecifierType)TypeSpecType}]</DisplayString>
   </Type>
   <Type Name="clang::PragmaHandler">
     <DisplayString>{Name,s}</DisplayString>
   </Type>
   <Type Name="clang::FileEntry">