[OPENMP50]Support for acquire clause.

Added full support for acquire clause in flush|atomic directives.
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index c25ce49..89b8e31 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -11669,6 +11669,9 @@
   case OMPC_acq_rel:
     C = new (Context) OMPAcqRelClause();
     break;
+  case OMPC_acquire:
+    C = new (Context) OMPAcquireClause();
+    break;
   case OMPC_threads:
     C = new (Context) OMPThreadsClause();
     break;
@@ -11933,6 +11936,8 @@
 
 void OMPClauseReader::VisitOMPAcqRelClause(OMPAcqRelClause *) {}
 
+void OMPClauseReader::VisitOMPAcquireClause(OMPAcquireClause *) {}
+
 void OMPClauseReader::VisitOMPThreadsClause(OMPThreadsClause *) {}
 
 void OMPClauseReader::VisitOMPSIMDClause(OMPSIMDClause *) {}