Ondřej Surý authored Oct 20, 2021 and Ondřej Surý committed Oct 21, 2021

The isc_time_add() could overflow when t.seconds + i.seconds == UINT_MAX
and t.nanoseconds + i.nanoseconds >= NS_PER_S.

Fix the overflow in isc_time_add(), and simplify the ISC_R_RANGE checks
both in isc_time_add() and isc_time_subtract() functions.