Slightly improve Visual Studio visualization of clang::Expr

Now it gives the StmtClass of the Expr as well as the type. It's still
a long way from full visualization of expressions, but I have found
that having the class really helps when debugging, so definitely
worth submitting.

llvm-svn: 271866
diff --git a/clang/utils/ClangVisualizers/clang.natvis b/clang/utils/ClangVisualizers/clang.natvis
index 97f0b0d..2b0a502 100644
--- a/clang/utils/ClangVisualizers/clang.natvis
+++ b/clang/utils/ClangVisualizers/clang.natvis
@@ -424,6 +424,6 @@
     </Expand>

   </Type>

   <Type Name="clang::Expr">

-    <DisplayString>Expression of type {TR,view(cpp)}</DisplayString>

+    <DisplayString>Expression of class {(clang::Stmt::StmtClass)StmtBits.sClass,en} and type {TR,view(cpp)}</DisplayString>

   </Type>

 </AutoVisualizer>