Always call update_use_power() instead of directly setting the use_power var.

- This will let us react to the change appropriately.
- While we're here, lets define some constants so we can stop using bare numbers.
- Always use those constants when calling update_use_power()

code/ATMOSPHERICS/components/binary_devices/dp_vent_pump.dm

@@ -214,10 +214,10 @@
 	if(!signal.data["tag"] || (signal.data["tag"] != id) || (signal.data["sigtype"]!="command"))
 		return 0
 	if(signal.data["power"])
-		use_power = text2num(signal.data["power"])
+		update_use_power(text2num(signal.data["power"]))
 
 	if(signal.data["power_toggle"])
-		use_power = !use_power
+		update_use_power(!use_power)
 
 	if(signal.data["direction"])
 		pump_direction = text2num(signal.data["direction"])

code/ATMOSPHERICS/components/binary_devices/pump.dm

@@ -160,12 +160,12 @@ Thus, the two variables affect pump operation are set in New():
 
 	if(signal.data["power"])
 		if(text2num(signal.data["power"]))
-			use_power = 1
+			update_use_power(USE_POWER_IDLE)
 		else
-			use_power = 0
+			update_use_power(USE_POWER_OFF)
 
 	if("power_toggle" in signal.data)
-		use_power = !use_power
+		update_use_power(!use_power)
 
 	if(signal.data["set_output_pressure"])
 		target_pressure = between(
@@ -199,7 +199,7 @@ Thus, the two variables affect pump operation are set in New():
 	if(..()) return 1
 
 	if(href_list["power"])
-		use_power = !use_power
+		update_use_power(!use_power)
 
 	switch(href_list["set_press"])
 		if ("min")