unix/modmachine: Add Signal class to machine module.

unix/modmachine.c

@@ -32,6 +32,7 @@
 
 #include "extmod/machine_mem.h"
 #include "extmod/machine_pinbase.h"
+#include "extmod/machine_signal.h"
 #include "extmod/machine_pulse.h"
 
 #if MICROPY_PLAT_DEV_MEM
@@ -82,6 +83,7 @@ STATIC const mp_rom_map_elem_t machine_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_mem32), MP_ROM_PTR(&machine_mem32_obj) },
 
     { MP_ROM_QSTR(MP_QSTR_PinBase), MP_ROM_PTR(&machine_pinbase_type) },
+    { MP_ROM_QSTR(MP_QSTR_Signal), MP_ROM_PTR(&machine_signal_type) },
     #if MICROPY_PY_MACHINE_PULSE
     { MP_ROM_QSTR(MP_QSTR_time_pulse_us), MP_ROM_PTR(&machine_time_pulse_us_obj) },
     #endif