performance issue - and easy fix #84

OCESQLSetResultParams take ~ 20% in some tested batch programs - and nearly all of this time is spend in add_sql_res_var_list. And ~15% of the cpu time is only spend in the following loop (here: line 2407)

The simple solution: add another var next to _sql_var_lists that contains the last current entry, set it likely only in the same function, use it instead of the loop. Result: 14% cpu time saved.