py/modthread: Add exit() function.

Simply raises the SystemExit exception.

py/modthread.c

@@ -144,11 +144,17 @@ STATIC mp_obj_t mod_thread_start_new_thread(size_t n_args, const mp_obj_t *args)
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_thread_start_new_thread_obj, 2, 3, mod_thread_start_new_thread);
 
+STATIC mp_obj_t mod_thread_exit(void) {
+    nlr_raise(mp_obj_new_exception(&mp_type_SystemExit));
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(mod_thread_exit_obj, mod_thread_exit);
+
 STATIC const mp_rom_map_elem_t mp_module_thread_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR__thread) },
     { MP_ROM_QSTR(MP_QSTR_get_ident), MP_ROM_PTR(&mod_thread_get_ident_obj) },
     { MP_ROM_QSTR(MP_QSTR_stack_size), MP_ROM_PTR(&mod_thread_stack_size_obj) },
     { MP_ROM_QSTR(MP_QSTR_start_new_thread), MP_ROM_PTR(&mod_thread_start_new_thread_obj) },
+    { MP_ROM_QSTR(MP_QSTR_exit), MP_ROM_PTR(&mod_thread_exit_obj) },
 };
 
 STATIC MP_DEFINE_CONST_DICT(mp_module_thread_globals, mp_module_thread_globals_table);