avoid being picked up by the DTrace fbt provider.
This is called by __udivdi3() for doing 64bit division on a 32bit arch and may
be called from within the dtrace context causing a double fault.
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.