adminvote.sma exploit fix (#823)

* Restrict having ".." character sequence in amx_votemap command arguments

Fixes exploit on Windows servers that allows executing potentially dangerous console commands

* Fix typo

containi -> contain

plugins/adminvote.sma

@@ -239,6 +239,9 @@ public cmdVoteMap(id, level, cid)
 	{
 		read_argv(i, g_optionName[g_validMaps], 31)
 
+		if (contain(g_optionName[g_validMaps], "..") != -1)
+			continue
+
 		if (is_map_valid(g_optionName[g_validMaps]))
 			g_validMaps++
 	}