Reduces penalty to movespeed from being cold

It kicks in at a lower body temp and the slowdown is less harsh. You move noticeably faster than space wind, which was the goal here.

code/__DEFINES/atmospherics.dm

@@ -110,3 +110,4 @@
 #define PRESSURE_SUIT_REDUCTION_COEFFICIENT 0.8		//This is how much (percentual) a suit with the flag STOPSPRESSUREDMAGE reduces pressure.
 #define PRESSURE_HEAD_REDUCTION_COEFFICIENT 0.4		//This is how much (percentual) a helmet/hat with the flag STOPSPRESSUREDMAGE reduces pressure.
 
+#define COLD_SLOWDOWN_FACTOR				20		//Humans are slowed by the difference between bodytemp and BODYTEMP_COLD_DAMAGE_LIMIT divided by this

code/modules/mob/living/carbon/human/species.dm

@@ -695,8 +695,8 @@
 
 			if((H.disabilities & FAT))
 				mspeed += 1.5
-			if(H.bodytemperature < 283.222)
-				mspeed += (283.222 - H.bodytemperature) / 10 * (grav+0.5)
+			if(H.bodytemperature < BODYTEMP_COLD_DAMAGE_LIMIT)
+				mspeed += (BODYTEMP_COLD_DAMAGE_LIMIT - H.bodytemperature) / COLD_SLOWDOWN_FACTOR
 
 			mspeed += speedmod