[MEDIUM] stick_table: move the server ID to a generic data type

The server ID is now stored just as any other data type. It is only
allocated if needed and is manipulated just like the other ones.
diff --git a/src/cfgparse.c b/src/cfgparse.c
index 26c8ba7..d472f99 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -4899,6 +4899,7 @@
 			else {
 				free((void *)mrule->table.name);
 				mrule->table.t = &(target->table);
+				stktable_alloc_data_type(&target->table, STKTABLE_DT_SERVER_ID);
 			}
 		}
 
@@ -4931,6 +4932,7 @@
 			else {
 				free((void *)mrule->table.name);
 				mrule->table.t = &(target->table);
+				stktable_alloc_data_type(&target->table, STKTABLE_DT_SERVER_ID);
 			}
 		}