[OPENMP50]Add support for 'release' clause.

Added full support for 'release' clause in flush|atomic directives.
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 89b8e31..c9553de 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -11672,6 +11672,9 @@
   case OMPC_acquire:
     C = new (Context) OMPAcquireClause();
     break;
+  case OMPC_release:
+    C = new (Context) OMPReleaseClause();
+    break;
   case OMPC_threads:
     C = new (Context) OMPThreadsClause();
     break;
@@ -11938,6 +11941,8 @@
 
 void OMPClauseReader::VisitOMPAcquireClause(OMPAcquireClause *) {}
 
+void OMPClauseReader::VisitOMPReleaseClause(OMPReleaseClause *) {}
+
 void OMPClauseReader::VisitOMPThreadsClause(OMPThreadsClause *) {}
 
 void OMPClauseReader::VisitOMPSIMDClause(OMPSIMDClause *) {}