watchdogd(8) and watchdog(4) enhancements.

The following support was added to watchdog(4):
- Support to query the outstanding timeout.
- Support to set a software pre-timeout function watchdog with an 'action'
- Support to set a software only watchdog with a configurable 'action'

'action' can be a mask specifying a single operation or a combination of:
 log(9), printf(9), panic(9) and/or kdb_enter(9).

Support the following in watchdogged:
- Support to utilize the new additions to watchdog(4).
- Support to warn if a watchdog script runs for too long.
- Support for "dry run" where we do not actually arm the watchdog,
  but only report on our timing.

Sponsored by:   iXsystems, Inc.
MFC after:      1 month