gdb/python: new gdb.architecture_names function

Add a new function to the Python API, gdb.architecture_names().  This
function returns a list containing all of the supported architecture
names within the current build of GDB.

The values returned in this list are all of the possible values that
can be returned from gdb.Architecture.name().

gdb/python/py-arch.c

@@ -271,6 +271,29 @@ archpy_register_groups (PyObject *self, PyObject *args)
   return gdbpy_new_reggroup_iterator (gdbarch);
 }
 
+/* Implementation of gdb.architecture_names().  Return a list of all the
+   BFD architecture names that GDB understands.  */
+
+PyObject *
+gdbpy_all_architecture_names (PyObject *self, PyObject *args)
+{
+  gdbpy_ref<> list (PyList_New (0));
+  if (list == nullptr)
+    return nullptr;
+
+  std::vector<const char *> name_list = gdbarch_printable_names ();
+  for (const char *name : name_list)
+    {
+      gdbpy_ref <> py_name (PyString_FromString (name));
+      if (py_name == nullptr)
+	return nullptr;
+      if (PyList_Append (list.get (), py_name.get ()) < 0)
+	return nullptr;
+    }
+
+ return list.release ();
+}
+
 void _initialize_py_arch ();
 void
 _initialize_py_arch ()