[OPENMP50]Support 'destroy' clause on 'depobj' directives.

Added basic support (parsing/sema/serialization) for 'destroy' clause in
depobj directives.
diff --git a/clang/lib/AST/OpenMPClause.cpp b/clang/lib/AST/OpenMPClause.cpp
index 888dc30..2bd02a0 100644
--- a/clang/lib/AST/OpenMPClause.cpp
+++ b/clang/lib/AST/OpenMPClause.cpp
@@ -143,6 +143,7 @@
   case OMPC_match:
   case OMPC_nontemporal:
   case OMPC_order:
+  case OMPC_destroy:
     break;
   }
 
@@ -228,6 +229,7 @@
   case OMPC_match:
   case OMPC_nontemporal:
   case OMPC_order:
+  case OMPC_destroy:
     break;
   }
 
@@ -1423,6 +1425,10 @@
   OS << ")";
 }
 
+void OMPClausePrinter::VisitOMPDestroyClause(OMPDestroyClause *) {
+  OS << "destroy";
+}
+
 template<typename T>
 void OMPClausePrinter::VisitOMPClauseList(T *Node, char StartSym) {
   for (typename T::varlist_iterator I = Node->varlist_begin(),