[OPENMP50]Add support for 'release' clause.

Added full support for 'release' clause in flush|atomic directives.
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 7263e65..eb79ba2 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -6151,6 +6151,8 @@
 
 void OMPClauseWriter::VisitOMPAcquireClause(OMPAcquireClause *) {}
 
+void OMPClauseWriter::VisitOMPReleaseClause(OMPReleaseClause *) {}
+
 void OMPClauseWriter::VisitOMPThreadsClause(OMPThreadsClause *) {}
 
 void OMPClauseWriter::VisitOMPSIMDClause(OMPSIMDClause *) {}