fuse should add uhelper= mount option to allow unmounting with umount

Hi,

mount -t fuse or -t fuse.sshfs calls mount.fuse and libfuse based fuse wrappers like sshfs or archivemount use fuse_main, but these mount points can't be unmounted with "umount".

There's provision to umount fses which aren't in fstab by non-root, but this requires setting an "uhelper" program.

I've tried this:
* mount with archivemount or mount.fuse as a regular user
* edit mtab and add "uhelper=fuse" in the mount options
* create a /sbin/umount.fuse shell script which just execs fusermount -u "$@"
this allowed me to "umount" as a regular user; I believe fuse should do so.

Also, why trying this out I noticed that fuse is looking for user=xyz in mtab, but can't cope with this not being the last option; this probably needs to be fixed if more options get appended to mtab.

Cheers,