[OPENMP50]Add support for relaxed clause in atomic directive.

Added full support for relaxed clause.
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index eb79ba2..f935a69 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -6153,6 +6153,8 @@
 
 void OMPClauseWriter::VisitOMPReleaseClause(OMPReleaseClause *) {}
 
+void OMPClauseWriter::VisitOMPRelaxedClause(OMPRelaxedClause *) {}
+
 void OMPClauseWriter::VisitOMPThreadsClause(OMPThreadsClause *) {}
 
 void OMPClauseWriter::VisitOMPSIMDClause(OMPSIMDClause *) {}