use ISC_REFCOUNT_IMPL for dns_xfrin_ctx_t (which has been renamed to dns_xfrin_t to keep the function names dns_xfrin_attach() and dns_xfrin_detach() unchanged).
use ISC_REFCOUNT_IMPL for dns_xfrin_ctx_t (which has been renamed to dns_xfrin_t to keep the function names dns_xfrin_attach() and dns_xfrin_detach() unchanged).