integrate XGM into the code

New turf proc: assume_gas().  Maps to air.adjust_gas_temp().
Lots of optimizations to processing, fire, lighting, HasEntered() and
 more.
Zones now process all fire data and existance in one go, fire objects
 only handle spreading.
Most code has been ported straight so some of it mightn't be ideally
 structured for the new gas_mixtures.

Signed-off-by: Mloc-Argent <colmohici@gmail.com>

code/game/objects/structures/crates_lockers/crates.dm

@@ -323,12 +323,7 @@
 		var/datum/gas_mixture/gas = (..())
 		if(!gas)	return null
 		var/datum/gas_mixture/newgas = new/datum/gas_mixture()
-		newgas.oxygen = gas.oxygen
-		newgas.carbon_dioxide = gas.carbon_dioxide
-		newgas.nitrogen = gas.nitrogen
-		newgas.phoron = gas.phoron
-		newgas.volume = gas.volume
-		newgas.temperature = gas.temperature
+		newgas.copy_from(gas)
 		if(newgas.temperature <= target_temp)	return
 
 		if((newgas.temperature - cooling_power) > target_temp)

code/game/objects/structures/mineral_doors.dm

@@ -206,15 +206,9 @@
 
 	proc/TemperatureAct(temperature)
 		for(var/turf/simulated/floor/target_tile in range(2,loc))
-
-			var/datum/gas_mixture/napalm = new
-
 			var/phoronToDeduce = temperature/10
+			target_tile.assume_gas("phoron", phoronToDeduce, 200+T0C)
 
-			napalm.phoron = phoronToDeduce
-			napalm.temperature = 200+T0C
-
-			target_tile.assume_air(napalm)
 			spawn (0) target_tile.hotspot_expose(temperature, 400)
 
 			hardness -= phoronToDeduce/100

code/game/objects/structures/transit_tubes.dm

@@ -81,8 +81,7 @@ obj/structure/ex_act(severity)
 /obj/structure/transit_tube_pod/New(loc)
 	..(loc)
 
-	air_contents.oxygen = MOLES_O2STANDARD * 2
-	air_contents.nitrogen = MOLES_N2STANDARD
+	air_contents.adjust_multi("oxygen", MOLES_O2STANDARD * 2, "nitrogen", MOLES_N2STANDARD)
 	air_contents.temperature = T20C
 
 	// Give auto tubes time to align before trying to start moving
@@ -123,8 +122,8 @@ obj/structure/ex_act(severity)
 			else if(!pod.moving && pod.dir in directions())
 				AM.loc = pod
 				return
-			
-			
+
+
 /obj/structure/transit_tube/station/attack_hand(mob/user as mob)
 	if(!pod_moving)
 		for(var/obj/structure/transit_tube_pod/pod in loc)
@@ -359,11 +358,7 @@ obj/structure/ex_act(severity)
 //  datum, there might be problems if I don't...
 /obj/structure/transit_tube_pod/return_air()
 	var/datum/gas_mixture/GM = new()
-	GM.oxygen			= air_contents.oxygen
-	GM.carbon_dioxide	= air_contents.carbon_dioxide
-	GM.nitrogen			= air_contents.nitrogen
-	GM.phoron			= air_contents.phoron
-	GM.temperature		= air_contents.temperature
+	GM.copy_from(air_contents)
 	return GM
 
 // For now, copying what I found in an unused FEA file (and almost identical in a
@@ -398,8 +393,8 @@ obj/structure/ex_act(severity)
 	var/transfer_in = max(0.1, 0.5 * (env_pressure - int_pressure) / total_pressure)
 	var/transfer_out = max(0.1, 0.3 * (int_pressure - env_pressure) / total_pressure)
 
-	var/datum/gas_mixture/from_env = loc.remove_air(environment.total_moles() * transfer_in)
-	var/datum/gas_mixture/from_int = air_contents.remove(air_contents.total_moles() * transfer_out)
+	var/datum/gas_mixture/from_env = loc.remove_air(environment.total_moles * transfer_in)
+	var/datum/gas_mixture/from_int = air_contents.remove(air_contents.total_moles * transfer_out)
 
 	loc.assume_air(from_int)
 	air_contents.merge(from_env)

code/game/objects/structures/watercloset.dm

@@ -190,7 +190,7 @@
 				del(mymist)
 				ismist = 0
 
-/obj/machinery/shower/HasEntered(atom/movable/O)
+/obj/machinery/shower/Crossed(atom/movable/O)
 	..()
 	wash(O)
 	if(ismob(O))