instead of including the userland string.h header.
Prompted by: breakage with old string.h from recent machine/types.h fix
Approved by: peter (in principle)
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.
