bzero for libc

["Martin J. Laubach" <mjl%netbsd.org@localhost>]

  I have reworked the bzero code to include the comments I
received (mainly it now fetches the machdep.cacheline sysctl
value instead of using a hardcoded value of 32), and generally
cleaned it up a bit. It now also includes memset and takes
advantage of the faster code path when the value is zero.

  Please give it a solid beating and brick me for any problems
found. I prefer that over breaking libc for all of us and then
being roasted over small flames :)

  You can find the current version at

         http://rhubarb.emsi.priv.at/download/bzero2.tar.gz

  Please go to basesrc/lib/libc/arch/powerpc/string, apply the
included patch and rebuild your libc. That should give you a
memset about twice as fast for the general case, and bzero
about four times faster.

        mjl