[Python] Add methods reference_value and const_value to gdb.Value.

gdb/ChangeLog:

	* NEWS (Python Scripting): Mention the new gdb.Value methods.
	* python/py-value.c (valpy_reference_value): New function.
	(valpy_const_value): Likewise.
	(value_object_methods): Add new methods.
	* value.c (make_cv_value): New function.
	* value.h (make_cv_value): Declare.

gdb/doc/ChangeLog:

	* python.texi (Values From Inferior): Add descriptions of new
	methods gdb.Value.reference_value and gdb.Value.const_value.

gdb/testsuite/ChangeLog:

	* gdb.python/py-xmethods.cc: Enhance test case.
	* gdb.python/py-xmethods.exp: New tests.
	* gdb.python/py-xmethods.py (A_indexoper): New xmethod worker
	function.
	(B_indexoper): Likewise.
	(global_dm_list) : Add new xmethod worker functions.

gdb/python/py-value.c

@@ -236,6 +236,59 @@ valpy_referenced_value (PyObject *self, PyObject *args)
   return result;
 }
 
+/* Return a value which is a reference to the value.  */
+
+static PyObject *
+valpy_reference_value (PyObject *self, PyObject *args)
+{
+  PyObject *result = NULL;
+
+  TRY
+    {
+      struct value *self_val;
+      struct cleanup *cleanup = make_cleanup_value_free_to_mark (value_mark ());
+
+      self_val = ((value_object *) self)->value;
+      result = value_to_value_object (value_ref (self_val));
+
+      do_cleanups (cleanup);
+    }
+  CATCH (except, RETURN_MASK_ALL)
+    {
+      GDB_PY_HANDLE_EXCEPTION (except);
+    }
+  END_CATCH
+
+  return result;
+}
+
+/* Return a "const" qualified version of the value.  */
+
+static PyObject *
+valpy_const_value (PyObject *self, PyObject *args)
+{
+  PyObject *result = NULL;
+
+  TRY
+    {
+      struct value *self_val, *res_val;
+      struct cleanup *cleanup = make_cleanup_value_free_to_mark (value_mark ());
+
+      self_val = ((value_object *) self)->value;
+      res_val = make_cv_value (1, 0, self_val);
+      result = value_to_value_object (res_val);
+
+      do_cleanups (cleanup);
+    }
+  CATCH (except, RETURN_MASK_ALL)
+    {
+      GDB_PY_HANDLE_EXCEPTION (except);
+    }
+  END_CATCH
+
+  return result;
+}
+
 /* Return "&value".  */
 static PyObject *
 valpy_get_address (PyObject *self, void *closure)
@@ -1692,6 +1745,10 @@ reinterpret_cast operator."
   { "dereference", valpy_dereference, METH_NOARGS, "Dereferences the value." },
   { "referenced_value", valpy_referenced_value, METH_NOARGS,
     "Return the value referenced by a TYPE_CODE_REF or TYPE_CODE_PTR value." },
+  { "reference_value", valpy_reference_value, METH_NOARGS,
+    "Return a value of type TYPE_CODE_REF referencing this value." },
+  { "const_value", valpy_const_value, METH_NOARGS,
+    "Return a 'const' qualied version of the same value." },
   { "lazy_string", (PyCFunction) valpy_lazy_string,
     METH_VARARGS | METH_KEYWORDS,
     "lazy_string ([encoding]  [, length]) -> lazy_string\n\