This system call was used in legacy Lisp code, that was inherited to modern
age and still compiled against supported compat layers (e.g. in clisp,
oaklisp, Franz Lisp).
It used to instruct the kernel about paging policy (G/C aware, flush etc).
Newly compiled code (assuming that it will detect vadvise()) will use the
libc stub for vadvise(). The headers for this interface are gone.
vadvise(2) could be marked as COMPAT_80, but as long as we support ultrix,
sunos or aout68k ABI, don't bother with this.
Requested by <mrg>
