New "timeout" api, to replace callout

[M. Warner Losh]

In message: <19827.1196612123 at critter.freebsd.dk>
            "Poul-Henning Kamp" <phk at phk.freebsd.dk> writes:
: In message <20071202.085545.177225588.imp at bsdimp.com>, "M. Warner Losh" writes:
: 
: >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.
: 
: Yes, but those can hardly be called "concrete" in terms of wanting
: to know what they mean, can they ? :-)
: 
: The only way I can see we can deal with them in the short term,
: is to ask for timeouts of "1000000 / hz, TIMEOUT_USEC"

Or have a "timeout_soon" function like you have the other timeout
conversion routines.

Warner