New "timeout" api, to replace callout

[M. Warner Losh]

In message: <19518.1196609689 at critter.freebsd.dk>
            "Poul-Henning Kamp" <phk at phk.freebsd.dk> writes:
: >"periodically with whatever period is convenient to you" is
: >a legitimate request that client code might have.
: >(I understand that this concept of time is very southern european :)
: 
: I disagree, that case, should be "with a period between N and M,
: at your choice".
: 
: And yes, it may be that we need to extend the API for that, but
: please give a concrete example so we know what we're talking about.

There are a number of places in the tree that use a parameter of '1'
today to mean "next time that's convenient."  Some of these places are
clever and know that HZ is never < 100 or > 1000 (or so they think),
while others are just sloppy code.

Warner