simpler /usr/bin/vi check
Also exclude /home
Mostly bugfixes of bugs triggered by the test set.

bugfixes:
 SYSTEM:
 . removed
        rc->p_priv->s_flags = 0;
   for the priv struct shared by all user processes in get_priv(). this
   should only be done once. doing a SYS_PRIV_USER in sys_privctl()
   caused the flags of all user processes to be reset, so they were no
   longer PREEMPTIBLE. this happened when RS executed a policy script.
   (this broke test1 in the test set)

 VFS/MFS:
 . chown can change the mode of a file, and chmod arguments are only
   part of the full file mode so the full filemode is slightly magic.
   changed these calls so that the final modes are returned to VFS, so
   that the vnode can be kept up-to-date.
   (this broke test11 in the test set)

 MFS:
 . lookup() checked for sizeof(string) instead of sizeof(user_path),
   truncating long path names
   (caught by test 23)
 . truncate functions neglected to update ctime
   (this broke test16)

 VFS:
 . corner case of an empty filename lookup caused fields of a request
   not to be filled in in the lookup functions, not making it clear
   that the lookup had failed, causing messages to garbage processes,
   causing strange failures.
   (caught by test 30)
 . trust v_size in vnode when doing reads or writes on non-special
   files, truncating i/o where necessary; this is necessary for pipes,
   as MFS can't tell when a pipe has been truncated without it being
   told explicitly each time.
   when the last reader/writer on a pipe closes, tell FS about
   the new size using truncate_vn().
   (this broke test 25, among others)
 . permission check for chdir() had disappeared; added a
   forbidden() call
   (caught by test 23)

new code, shouldn't change anything:
 . introduced RTS_SET, RTS_UNSET, and RTS_ISSET macro's, and their
   LOCK variants. These macros set and clear the p_rts_flags field,
   causing a lot of duplicated logic like

       old_flags = rp->p_rts_flags;            /* save value of the flags */
       rp->p_rts_flags &= ~NO_PRIV;
       if (old_flags != 0 && rp->p_rts_flags == 0) lock_enqueue(rp);

   to change into the simpler

       RTS_LOCK_UNSET(rp, NO_PRIV);

   so the macros take care of calling dequeue() and enqueue() (or lock_*()),
   as the case may be). This makes the code a bit more readable and a
   bit less fragile.
 . removed return code from do_clocktick in CLOCK as it currently
   never replies
 . removed some debug code from VFS
 . fixed grant debug message in device.c
 
preemptive checks, tests, changes:
 . added return code checks of receive() to SYSTEM and CLOCK
 . O_TRUNC should never arrive at MFS (added sanity check and removed
   O_TRUNC code)
 . user_path declared with PATH_MAX+1 to let it be null-terminated
 . checks in MFS to see if strings passed by VFS are null-terminated
 
 IS:
 . static irq name table thrown out
Retired DEV_{READ,WRITE,GATHER,SCATTER,IOCTL} (safe versions *_S are to
be used and drivers should never receieve these 'unsafe' variants
any more).
Sanity check in clock - process is supposed to be runnable when it's
interrupted.
Make /dev/c1* device nodes on disk and on the boot ramdisk.

 . include c1* nodes in std in MAKEDEV
 . this requires a slightly larger shell
 . this requires a larger blocksize on the boot ramdisk (to fit
   /dev/ in direct blocks for mkfs with a proto file)
 . also more inodes and kB's on the boot ramdisk
Start a 2nd copy of at_wini, for /dev/c1*. This requires a slightly
larger rs.
supply instance to 2nd at_wini instance.
requires a little cooperation from at_wini.
Extend cdprobe probe list to c1, and reorder minors to do most-likely
first.

Make at_wini include instance number in error messages.
Use temporary binary directory as bootstrap
don't call mkdep with an absolute path
include /usr/xbin bootstrap dir in $PATH
Fixes for /usr/xbin binaries bootstrap dir.
use shorter ata timeout for identify commands when running from cd
to shorten probe time.
Memory requirements a bit more now with mfs processes
Don't complain about missing ip address.
Typo's.
mkfs needs more memory for the boot ramdisk.
set 'w_testing' during w_identify(). this means 0-tolerance to
timeouts, and an ATA_IDENTIFY timeout will cause the ATAPI_IDENTIFY
to be skipped, making the cd probe a lot faster.
removed or optionalized verbose/debugging messages