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.
All new code is "#ifdef PC98"ed so this should make no difference to
PC/AT (and its clones) users.
Ok'd by: core
Submitted by: FreeBSD(98) development team
msdosfs_lookup() did no validation to see if the caller was validated
to delete/rename/create files. msdosfs_setattr() did no validation
to see if the caller was allowed to change the file permissions (turn
on/off the write bit) or update the file modification time (utimes).
The routines were fixed to validate the calls just like ufs does.
