fixed %c for jstrftime using Gregorian weekday names instead of Farsi. unnecessary in_buf modifications removed from re-entrant _r() versions for date/time modification functions. jmktime() uses jalali_update() to normalize jtm struct. jstrftime %s now uses a temporary jtm struct to get unix timestamp as jmktime(struct jtm*) violates it's jtm supplied data constness and jstrftime signature enforces a const jtm data to be supplied.