critical-min and critical-max; also, a battery warning-capacity is
added in addition to a critical-capacity.
2. usr.sbin/envstat is modified to introduce a -W command line switch to
display the warning-* values instead of the critical-* values, and
envstat(8) and envsys.conf(5) man pages are updated appropriately.
3. Treat user-defined limits as a single continuum and generate a single
event regardless of how many boundaries a change in sensor value
crosses; ditto for driver-defined limits.
Fixes my PR/39021
Fixes my PR/39022
OK'd by christos@ bouyer@ cube@
6d65ba8398