[OPENMP50]Add initial support for OpenMP 5.0 iterator.

Added basic parsing/semantic analysis/(de)serialization support for
iterator expression introduced in OpenMP 5.0.
diff --git a/clang/lib/Sema/SemaExceptionSpec.cpp b/clang/lib/Sema/SemaExceptionSpec.cpp
index fad2ae1..0dc0c68 100644
--- a/clang/lib/Sema/SemaExceptionSpec.cpp
+++ b/clang/lib/Sema/SemaExceptionSpec.cpp
@@ -1300,6 +1300,7 @@
   case Expr::ArraySubscriptExprClass:
   case Expr::OMPArraySectionExprClass:
   case Expr::OMPArrayShapingExprClass:
+  case Expr::OMPIteratorExprClass:
   case Expr::BinaryOperatorClass:
   case Expr::DependentCoawaitExprClass:
   case Expr::CompoundAssignOperatorClass: