[c++20] Add CXXRewrittenBinaryOperator to represent a comparison
operator that is rewritten as a call to multiple other operators.

No functionality change yet: nothing creates these expressions.

llvm-svn: 375305
diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index f2e6251..3438c3a 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -3473,6 +3473,7 @@
   case ArrayInitLoopExprClass:
   case ParenListExprClass:
   case CXXPseudoDestructorExprClass:
+  case CXXRewrittenBinaryOperatorClass:
   case CXXStdInitializerListExprClass:
   case SubstNonTypeTemplateParmExprClass:
   case MaterializeTemporaryExprClass: