[OPENMP50]Add basic support for depobj construct.

Added basic parsing/sema/serialization support for depobj directive.
diff --git a/clang/lib/Sema/SemaExceptionSpec.cpp b/clang/lib/Sema/SemaExceptionSpec.cpp
index 193eaa3..1e892aa 100644
--- a/clang/lib/Sema/SemaExceptionSpec.cpp
+++ b/clang/lib/Sema/SemaExceptionSpec.cpp
@@ -1430,6 +1430,7 @@
   case Stmt::OMPDistributeParallelForSimdDirectiveClass:
   case Stmt::OMPDistributeSimdDirectiveClass:
   case Stmt::OMPFlushDirectiveClass:
+  case Stmt::OMPDepobjDirectiveClass:
   case Stmt::OMPForDirectiveClass:
   case Stmt::OMPForSimdDirectiveClass:
   case Stmt::OMPMasterDirectiveClass: