Revert "- Make callout(9) tickless, relying on eventtimers(4) as backend for"

This reverts commit cce7b765e00c0893a5f7999806f09a9b7ce4e1c7.
Revert "MFcalloutng:"

This reverts commit 75c21f83b2e459b240bf49c095a624700745744f.
Revert "Make load average sampling asynchronous to hardclock ticks. This improves"

This reverts commit d7bb9d3c054b131f96c84c609fbdafb45568f431.
Revert "MFcalloutng (r244355):"

This reverts commit f99a9b2f232bb46f05ac3599fe2fcf2fea5eb1ea.
Revert "MFcalloutng:"

This reverts commit a3afa89db03d2a1e3d119467bdcc1d9710cf8456.
Revert "MFcalloutng:"

This reverts commit abd6e00f0218f243fa67c1a23c4ab5620c9d0dff.
Revert "Make dummynet use new direct callout(9) execution mechanism.  Since the only"

This reverts commit d6a70e77f983abff05ab836f2bbdb901c3ec6bf3.
Revert "MFcalloutng:"

This reverts commit 7315d8f6e26b0ab65b1f7e6165d3163b593a1fb4.
Revert "MFcalloutng (r247427 by mav):"

This reverts commit 376c2c1220910bbd37a9f657d951e943c633b59a.
Revert "MFcalloutng:"

This reverts commit 9bcd96fe9a601875bd0721e71d09e9636b78b3c2.
Revert "Move the definition of sbintime_t type from <sys/time.h> to <sys/types.h>."

This reverts commit ac0bdd238c6b4c2e9269e2e1bfcf399ce714938c.
Revert "Introduce sbintime_t type -- the simplified version of struct bintime,"

This reverts commit a05277079cdaa6d54e94f53c7e76fe236d6edd7c.
Adapt ZFS to the legacy callout implementation.