[OPENMP50]Add support for extended device clause in target directives.

Added parsing/sema/serialization support for extended device clause in
executable target directives.
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index b549fe9..c96e465 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -6376,7 +6376,9 @@
 
 void OMPClauseWriter::VisitOMPDeviceClause(OMPDeviceClause *C) {
   VisitOMPClauseWithPreInit(C);
+  Record.writeEnum(C->getModifier());
   Record.AddStmt(C->getDevice());
+  Record.AddSourceLocation(C->getModifierLoc());
   Record.AddSourceLocation(C->getLParenLoc());
 }