[clang][AST] TextNodeDumper: dump the operator spelling for overloaded operators.

This mirrors what is done for built-in operators.
diff --git a/clang/lib/AST/TextNodeDumper.cpp b/clang/lib/AST/TextNodeDumper.cpp
index 72f0ba3..84f9738 100644
--- a/clang/lib/AST/TextNodeDumper.cpp
+++ b/clang/lib/AST/TextNodeDumper.cpp
@@ -715,6 +715,14 @@
     OS << " adl";
 }
 
+void TextNodeDumper::VisitCXXOperatorCallExpr(const CXXOperatorCallExpr *Node) {
+  const char *OperatorSpelling = clang::getOperatorSpelling(Node->getOperator());
+  if (OperatorSpelling)
+    OS << " '" << OperatorSpelling << "'";
+
+  VisitCallExpr(Node);
+}
+
 void TextNodeDumper::VisitCastExpr(const CastExpr *Node) {
   OS << " <";
   {