To set things up to create a filesystem:

* the files fsproto.h, lock.h, and cache.h are private
  headers and will change in the future.  they are here
  only so you can develop file systems now. 

* if you intend to use the IDE for your development you
  will need to delete the sym link _KERNEL_ and instead
  copy /boot/beos/system/kernel_mac into this directory
  and call it _KERNEL_  (this is because the IDE can't 
  deal with a symlink to a kernel but the command line
  tools can).

* modify kernel_interface.c to suit your filesystem

* run the makefile.  it puts a copy of the file system
  into ~/config/add-ons/kernel/file_systems.  Then you
  have to mount your file system using the mount tool
  in the shell (with the "-t fstype" argument to specify
  your file system).
