[OPENMP50]Bassic support for exclusive clause.

Added basic support (parsing/sema/serialization) for exclusive clause in
scan directives.
diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index e05829f..bef36bf 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -4617,6 +4617,7 @@
   case OMPC_destroy:
   case OMPC_detach:
   case OMPC_inclusive:
+  case OMPC_exclusive:
     llvm_unreachable("Clause is not allowed in 'omp atomic'.");
   }
 }