[OPENMP50]Initial support for detach clause in task directive.

Added parsing/sema/serialization support for detach clause.
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 1278841..b549fe9 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -6096,6 +6096,11 @@
   Record.AddSourceLocation(C->getLParenLoc());
 }
 
+void OMPClauseWriter::VisitOMPDetachClause(OMPDetachClause *C) {
+  Record.AddStmt(C->getEventHandler());
+  Record.AddSourceLocation(C->getLParenLoc());
+}
+
 void OMPClauseWriter::VisitOMPDefaultClause(OMPDefaultClause *C) {
   Record.push_back(unsigned(C->getDefaultKind()));
   Record.AddSourceLocation(C->getLParenLoc());