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

Added basic support (parsing/sema/serialization) for 'destroy' clause in
depobj directives.
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 3a8b32c..865a666 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -11827,6 +11827,9 @@
   case OMPC_order:
     C = new (Context) OMPOrderClause();
     break;
+  case OMPC_destroy:
+    C = new (Context) OMPDestroyClause();
+    break;
   }
   assert(C && "Unknown OMPClause type");
 
@@ -11955,6 +11958,8 @@
 
 void OMPClauseReader::VisitOMPNogroupClause(OMPNogroupClause *) {}
 
+void OMPClauseReader::VisitOMPDestroyClause(OMPDestroyClause *) {}
+
 void OMPClauseReader::VisitOMPUnifiedAddressClause(OMPUnifiedAddressClause *) {}
 
 void OMPClauseReader::VisitOMPUnifiedSharedMemoryClause(