[BusyBox] Filesystem detection in mount & lazy unmount

[Chris Spiegel]

Hi,
  "mount" from mainline util-linux has the ability to do automatic filesystem 
detection, if no type is selected, by checking magic numbers - this is more 
complete than just checking /proc/filesystems because it can detect 
filesystems whose modules are not loaded.  When it tries to mount, then, the 
module automatically loads.  I find this to be a very handy feature.  SGI's 
xfsprogs has a small implementation of the filesystem detection that weigs in 
at about 5K compiled, on my system.  Would this be a useful addition to 
busybox?  If so, I'd be happy to integrate the code into busybox.

Also regarding mainline util-linux, umount has the ability to do a "lazy" 
unmount - it registers the unmount, and as soon as the filesystem isn't being 
used anymore, it's actually unmounted.  As with the above, I'm willing to add 
this feature if it's deemed appropriate.

Chris