[coroutines] Add overloaded unary 'operator co_await'.

llvm-svn: 250991
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 64f9ccd..86bc8e6 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -1753,6 +1753,9 @@
   // The conditional operator can't be overloaded, but we still handle it when
   // mangling expressions.
   case OO_Conditional: Out << "qu"; break;
+  // Proposal on cxx-abi-dev, 2015-10-21.
+  //              ::= aw        # co_await
+  case OO_Coawait: Out << "aw"; break;
 
   case OO_None:
   case NUM_OVERLOADED_OPERATORS: