Upgrade submodule, update code accordingly.

The gdb procedure varobj_delete() has dropped the "returned variable list"
feature, thus we can no longer use it to remove our tcl alias variables.
A new procedure variable_delete_tcl() is thus implemented to perform this
task before removing the gdb variable.

* gdbtk/generic/gdbtk_varobj.c: new procedure variable_delete_tcl().
  (variable_delete): remove tcl alias variable using variable_delete_tcl().

gdbtk/generic/gdbtk-varobj.c

@@ -1,5 +1,5 @@
 /* Variable user interface layer for GDB, the GNU debugger.
-   Copyright (C) 1999-2015 Free Software Foundation, Inc.
+   Copyright (C) 1999-2016 Free Software Foundation, Inc.
 
    This file is part of GDB.
 
@@ -400,26 +400,38 @@ variable_create (Tcl_Interp *interp, int objc, Tcl_Obj *CONST objv[])
   return TCL_ERROR;
 }
 
-/* Delete the variable object VAR and its children */
-/* If only_children_p, Delete only the children associated with the object. */
+/* Delete tcl representation of variable. */
 static void
-variable_delete (Tcl_Interp *interp, struct varobj *var,
-		 int only_children_p)
+variable_delete_tcl (Tcl_Interp *interp, struct varobj *var,
+                     int only_children_p)
 {
-  char **dellist;
-  char **vc;
-
-  varobj_delete (var, &dellist, only_children_p);
+  int i;
 
-  vc = dellist;
-  while (*vc != NULL)
+  /* Delete children. */
+  for (i = 0; i < VEC_length (varobj_p, var->children); i++)
     {
-      uninstall_variable (interp, *vc);
-      xfree (*vc);
-      vc++;
+      varobj_p child = VEC_index (varobj_p, var->children, i);
+
+      if (!child)
+        continue;
+      variable_delete_tcl (interp, child, 0);
     }
 
-  xfree (dellist);
+  if (only_children_p || !var->obj_name)
+    return;
+
+  /* Delete tcl variable now. */
+  uninstall_variable (interp, var->obj_name);
+}
+
+/* Delete the variable object VAR and its children */
+/* If only_children_p, Delete only the children associated with the object. */
+static void
+variable_delete (Tcl_Interp *interp, struct varobj *var,
+		 int only_children_p)
+{
+  variable_delete_tcl (interp, var, only_children_p);
+  varobj_delete (var, only_children_p);
 }
 
 /* Return a list of all the children of VAR, creating them if necessary. */