Add isc_tquota - a time based quota API
The new isc_tquota API uses isc_time_cputime() to count how much time we spent in a thread and returns ISC_R_SUCCESS, ISC_R_SOFTQUOTA or ISC_R_QUOTA based on the initialized values for soft and hard quotas. The soft quota can be skipped.
Edited by Ondřej Surý