Cleans up slipping code

Puts slipping into one proc rather than being dealt with individually by
each item.

The only changes to functionality here are where it would have been
possible to slip on some items whilst flying. It will make any changes
decided on in #3490 or any future changes far more easy to implement

code/game/objects/effects/effect_system.dm

@@ -985,16 +985,8 @@ steam.start() -- spawns the effect
 		return
 
 	if (istype(AM, /mob/living/carbon))
-		var/mob/M =	AM
-		if (istype(M, /mob/living/carbon/human) && (istype(M:shoes, /obj/item/clothing/shoes) && M:shoes.flags&NOSLIP) || M.buckled)
-			return
-		if (istype (M, /mob/living/carbon/human) && M:species.bodyflags & FEET_NOSLIP)
-			return
-		M.stop_pulling()
-		M << "\blue You slipped on the foam!"
-		playsound(src.loc, 'sound/misc/slip.ogg', 50, 1, -3)
-		M.Stun(5)
-		M.Weaken(2)
+		var/mob/living/carbon/M =	AM
+		M.slip("foam", 5, 2)
 
 
 /datum/effect/system/foam_spread

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

@@ -1214,19 +1214,8 @@ var/global/list/obj/item/device/pda/PDAs = list()
 
 /obj/item/device/pda/clown/Crossed(AM as mob|obj) //Clown PDA is slippery.
 	if (istype(AM, /mob/living/carbon))
-		var/mob/M =	AM
-		if ((istype(M, /mob/living/carbon/human) && (istype(M:shoes, /obj/item/clothing/shoes) && M:shoes.flags&NOSLIP)) || M.m_intent == "walk")
-			return
-
-		if ((istype(M, /mob/living/carbon/human) && (M.real_name != src.owner) && (istype(src.cartridge, /obj/item/weapon/cartridge/clown))))
-			if (src.cartridge.charges < 5)
-				src.cartridge.charges++
-
-		M.stop_pulling()
-		M << "\blue You slipped on the PDA!"
-		playsound(src.loc, 'sound/misc/slip.ogg', 50, 1, -3)
-		M.Stun(8)
-		M.Weaken(5)
+		var/mob/living/carbon/M =	AM
+		M.slip("pda", 8, 5, 0, 1)
 
 /obj/item/device/pda/proc/available_pdas()
 	var/list/names = list()

code/game/objects/items/weapons/clown_items.dm

@@ -22,36 +22,16 @@
 
 /obj/item/weapon/bananapeel/Crossed(AM as mob|obj)
 	if (istype(AM, /mob/living/carbon))
-		var/mob/M =	AM
-		if (istype(M, /mob/living/carbon/human) && (isobj(M:shoes) && M:shoes.flags&NOSLIP) || M.buckled)
-			return
-		if(istype(M, /mob/living/carbon/human) && M:species.bodyflags & FEET_NOSLIP)
-			return
-		if(M.flying)
-			return
-
-		M.stop_pulling()
-		M << "\blue You slipped on the [name]!"
-		playsound(src.loc, 'sound/misc/slip.ogg', 50, 1, -3)
-		M.Stun(4)
-		M.Weaken(2)
+		var/mob/living/carbon/M =	AM
+		M.slip("banana peel", 4, 2)
 
 /*
  * Soap
  */
 /obj/item/weapon/soap/Crossed(AM as mob|obj) //EXACTLY the same as bananapeel for now, so it makes sense to put it in the same dm -- Urist
 	if (istype(AM, /mob/living/carbon))
-		var/mob/M =	AM
-		if (istype(M, /mob/living/carbon/human) && (isobj(M:shoes) && M:shoes.flags&NOSLIP) || M.buckled)
-			return
-		if(M.flying)
-			return
-
-		M.stop_pulling()
-		M << "\blue You slipped on the [name]!"
-		playsound(src.loc, 'sound/misc/slip.ogg', 50, 1, -3)
-		M.Stun(4)
-		M.Weaken(2)
+		var/mob/living/carbon/M = AM
+		M.slip("soap", 4, 2)
 
 /obj/item/weapon/soap/afterattack(atom/target, mob/user as mob, proximity)
 	if(!proximity) return

code/game/objects/items/weapons/grenades/clowngrenade.dm

@@ -62,8 +62,8 @@
 
 	Crossed(AM as mob|obj)
 		var/burned = rand(2,5)
-		if(istype(AM, /mob/living))
-			var/mob/living/M = AM
+		if(istype(AM, /mob/living/carbon))
+			var/mob/living/carbon/M = AM
 			if(ishuman(M))
 				if(isobj(M:shoes))
 					if((M:shoes.flags&NOSLIP) || (M:species.bodyflags & FEET_NOSLIP))
@@ -73,16 +73,8 @@
 					M.take_overall_damage(0, max(0, (burned - 2)))
 
 			if(!istype(M, /mob/living/carbon/slime) && !isrobot(M))
-				M.stop_pulling()
-				step(M, M.dir)
-				spawn(1) step(M, M.dir)
-				spawn(2) step(M, M.dir)
-				spawn(3) step(M, M.dir)
-				spawn(4) step(M, M.dir)
+				M.slip("banana peel!", 0, 7, 4)
 				M.take_organ_damage(2) // Was 5 -- TLE
-				M << "\blue You slipped on \the [name]!"
-				playsound(src.loc, 'sound/misc/slip.ogg', 50, 1, -3)
-				M.Weaken(7)
 				M.take_overall_damage(0, burned)
 
 	throw_impact(atom/hit_atom)