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

Added full support for relaxed clause.
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index c9553de..a1161d2 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -11675,6 +11675,9 @@
   case OMPC_release:
     C = new (Context) OMPReleaseClause();
     break;
+  case OMPC_relaxed:
+    C = new (Context) OMPRelaxedClause();
+    break;
   case OMPC_threads:
     C = new (Context) OMPThreadsClause();
     break;
@@ -11943,6 +11946,8 @@
 
 void OMPClauseReader::VisitOMPReleaseClause(OMPReleaseClause *) {}
 
+void OMPClauseReader::VisitOMPRelaxedClause(OMPRelaxedClause *) {}
+
 void OMPClauseReader::VisitOMPThreadsClause(OMPThreadsClause *) {}
 
 void OMPClauseReader::VisitOMPSIMDClause(OMPSIMDClause *) {}