Implement the sizeof...(pack) expression to compute the length of a
parameter pack.

Note that we're missing proper libclang support for the new
SizeOfPackExpr expression node.

llvm-svn: 122813
diff --git a/clang/lib/AST/ExprClassification.cpp b/clang/lib/AST/ExprClassification.cpp
index f437804..a9ebe6f 100644
--- a/clang/lib/AST/ExprClassification.cpp
+++ b/clang/lib/AST/ExprClassification.cpp
@@ -151,6 +151,7 @@
   case Expr::ObjCStringLiteralClass:
   case Expr::ParenListExprClass:
   case Expr::InitListExprClass:
+  case Expr::SizeOfPackExprClass:
     return Cl::CL_PRValue;
 
     // Next come the complicated cases.