file writing bug

[CENT%MIT-OZ@MIT-MC.ARPA]

i'm not sure who can best solve this. when i am editing a file, and
write it back out to the same file name with same version number, the
not-backed-up bit doesn't get turned on. i assume this means that the
file, although changed, doesn't get saved in another incremental dump.
this is a loss; if the file gets written to the same name&version with
changed contents, the not-backed-up bit should get turned on so the
file's new contents can get saved on tape.