[Fix] Multimap: Fix operating with userdata

src/lua/lua_ip.c

 	LUA_INTERFACE_DEF (ip, apply_mask),
 	LUA_INTERFACE_DEF (ip, copy),
 	LUA_INTERFACE_DEF (ip, is_local),
+	{"tostring", lua_ip_to_string},
+	{"totable", lua_ip_to_table},
+	{"tonumber", lua_ip_to_number},
 	{"__tostring", lua_ip_to_string},
 	{"__eq", lua_ip_equal},
 	{"__gc", lua_ip_destroy},

src/plugins/lua/multimap.lua

     if r['cdb'] then
       local srch = value
       if type(value) == 'userdata' then
-        srch = value:to_string()
+        if value.class == 'rspamd{ip}' then
+          srch = value:tostring()
+        end
       end
       ret = r['cdb']:lookup(srch)
     elseif r['redis_key'] then
       local srch = {value}
       local cmd = 'HGET'
-      if type(value) == 'userdata' then
-        srch = {value:to_string()}
+      if type(value) == 'userdata' and value.class == 'rspamd{ip}' then
+        srch = {value:tostring()}
         cmd = 'HMGET'
         local maxbits = 128
         local minbits = 32
             minbits = 8
         end
         for i=maxbits,minbits,-1 do
-            local nip = value:apply_mask(i):to_string() .. "/" .. i
+            local nip = value:apply_mask(i):tostring() .. "/" .. i
             table.insert(srch, nip)
         end
       end
       ret = r['radix']:get_key(value)
     elseif r['hash'] then
       if type(value) == 'userdata' then
-        value = value:to_string()
+        if value.class == 'rspamd{ip}' then
+          value = value:tostring()
+        end
       end
       ret = r['hash']:get_key(value)
     end