add_func

create a function
     start, end - function bounds
                  If the function end address is BADADDR, then
                  IDA will try to determine the function bounds
                  automatically. IDA will define all necessary
                  instructions to determine the function bounds.
returns: !=0 - ok
note: an instruction should be present at the start address

success add_func(long start, long end=BADADDR);