esp8266/modmachine: Add Signal class.

esp8266/modmachine.c

@@ -31,6 +31,7 @@
 #include "py/obj.h"
 #include "py/runtime.h"
 #include "extmod/machine_mem.h"
+#include "extmod/machine_signal.h"
 #include "extmod/machine_pulse.h"
 #include "extmod/machine_i2c.h"
 #include "modmachine.h"
@@ -251,6 +252,7 @@ STATIC const mp_rom_map_elem_t machine_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_Timer), MP_ROM_PTR(&esp_timer_type) },
     { MP_ROM_QSTR(MP_QSTR_WDT), MP_ROM_PTR(&esp_wdt_type) },
     { MP_ROM_QSTR(MP_QSTR_Pin), MP_ROM_PTR(&pyb_pin_type) },
+    { MP_ROM_QSTR(MP_QSTR_Signal), MP_ROM_PTR(&machine_signal_type) },
     { MP_ROM_QSTR(MP_QSTR_PWM), MP_ROM_PTR(&pyb_pwm_type) },
     { MP_ROM_QSTR(MP_QSTR_ADC), MP_ROM_PTR(&pyb_adc_type) },
     { MP_ROM_QSTR(MP_QSTR_UART), MP_ROM_PTR(&pyb_uart_type) },