[OPENMP50]Add basic support for depobj construct.

Added basic parsing/sema/serialization support for depobj directive.
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 6f77d4f..fcc0b98 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -6342,6 +6342,11 @@
     Record.AddStmt(VE);
 }
 
+void OMPClauseWriter::VisitOMPDepobjClause(OMPDepobjClause *C) {
+  Record.AddStmt(C->getDepobj());
+  Record.AddSourceLocation(C->getLParenLoc());
+}
+
 void OMPClauseWriter::VisitOMPDependClause(OMPDependClause *C) {
   Record.push_back(C->varlist_size());
   Record.push_back(C->getNumLoops());