Fix group attack for slime, zombie and zombiepig

mods/ENTITIES/mcl_mobs/api.lua

@@ -2569,12 +2569,20 @@ local mob_punch = function(self, hitter, tflp, tool_capabilities, dir)
 
 			if obj then
 
-				-- only alert members of same mob
-				if obj.group_attack == true
+				-- only alert members of same mob or friends
+				if obj.group_attack
 				and obj.state ~= "attack"
-				and obj.owner ~= name
-				and obj.name == self.name then
-					do_attack(obj, hitter)
+				and obj.owner ~= name then
+					if obj.name == self.name then
+						do_attack(obj, hitter)
+					elseif type(obj.group_attack) == "table" then
+						for i=1, #obj.group_attack do
+							if obj.name == obj.group_attack[i] then
+								do_attack(obj, hitter)
+								break
+							end
+						end
+					end
 				end
 
 				-- have owned mobs attack player threat

mods/ENTITIES/mcl_mobs/api.txt

@@ -78,6 +78,8 @@ functions needed for the mob to work properly which contains the following:
                          punches when nearby.
    'group_attack'        when true has same mob type grouping together to attack
                          offender.
+                         [MCL2 extension:] When a table, this is a list of
+                         mob types that will get alerted as well (besides same mob type)
    'attack_type'         tells the api what a mob does when attacking the player
                          or another mob:
       'dogfight'         is a melee attack when player is within mob reach.
@@ -222,6 +224,7 @@ functions needed for the mob to work properly which contains the following:
       'glow' same as in entity definition
       'child' if true, spawn mob as child
 
+
 Node Replacement
 ----------------