* time/mktime.c (__mktime_internal): When the requested time falls
in a spring-forward gap of size DT, return a time that is DT away
from the requested time, preferring a time whose tm_isdst differs
from the requested value. Bump the max number of probes from 4 to
6 to account for the extra probes needed to discover a
spring-forward gap in the worst case.