Saycode refactor/improvements

- Refactored multiple bits of saycode to be less eyeburning code
 - Radios now properly report special channel messages (binary, hivemind)
 - Animals with no speak list no longer show unfiltered messages to
   everyone.

 - Fun part:
   - Improves handling of headsets for the two ear system.
     - The right headset will now be talked into if the left headset
       reports that it is unable to send the message on the chosen
       channel/mode.
     - This means that instead of having to swap headsets around, wearing
       a headset on either ear will grant you access to all of it's
       channels.
     - The left headset will take priority, which really only affects when
       it's set to a non-standard frequency.

code/game/objects/items/devices/radio/headset.dm

@@ -55,10 +55,12 @@
 		if(translate_binary)
 			var/datum/language/binary = all_languages["Robot Talk"]
 			binary.broadcast(M, message)
+			return RADIO_CONNECTION_NON_SUBSPACE
 		if(translate_hive)
 			var/datum/language/hivemind = all_languages["Hivemind"]
 			hivemind.broadcast(M, message)
-		return null
+			return RADIO_CONNECTION_NON_SUBSPACE
+		return RADIO_CONNECTION_FAIL
 
 	return ..()
 

code/game/objects/items/devices/radio/radio.dm

@@ -295,12 +295,14 @@ var/global/list/default_medbay_channels = list(
 			return secure_radio_connections[message_mode]
 
 	// If we were to send to a channel we don't have, drop it.
-	return null
+	return RADIO_CONNECTION_FAIL
 
 /obj/item/device/radio/talk_into(mob/living/M as mob, message, channel, var/verb = "says", var/datum/language/speaking = null)
-	if(!on) return 0 // the device has to be on
+	if(!on)
+		return 0 // the device has to be on
 	//  Fix for permacell radios, but kinda eh about actually fixing them.
-	if(!M || !message) return 0
+	if(!M || !message)
+		return 0
 
 	//  Uncommenting this. To the above comment:
 	// 	The permacell radios aren't suppose to be able to transmit, this isn't a bug and this "fix" is just making radio wires useless. -Giacom
@@ -322,12 +324,17 @@ var/global/list/default_medbay_channels = list(
 	*/
 
 	//#### Grab the connection datum ####//
-	var/datum/radio_frequency/connection = handle_message_mode(M, message, channel)
-	if(!istype(connection))
-		return 0
-	if(!connection)
+	var/message_mode = handle_message_mode(M, message, channel)
+	switch(message_mode) //special cases
+		if(RADIO_CONNECTION_FAIL)
+			return 0
+		if(RADIO_CONNECTION_NON_SUBSPACE)
+			return 1
+
+	if(!istype(message_mode, /datum/radio_frequency)) //if not a special case, it should be returning a radio connection
 		return 0
 
+	var/datum/radio_frequency/connection = message_mode
 	var/turf/position = get_turf(src)
 
 	//#### Tagging the signal with all appropriate identity values ####//