WIP: test back-end; loads and replays synthetic events from a directory.
Sanity-check an ACL when loaded.  Move passwd/groups parsing to
util.cpp.
Add sanity-checking to action parser.
Free up vdev_config fully.
We need to call mknod() and unlink() in a separate *process* from the
FUSE filesystem.  So, fork into a front-end filesystem and back-end
event dispatcher, and have the event dispatcher perform the requisite
operations.
Add lifecycle management for front-end and back-end vdev processes.
Apply ACLs on stat() and readdir()
Use proper regexec() and regcomp() flags.
Handle FUSE options in opts to create a separate FUSE-specific arguments
vector.  Add logic for opts lifecycle management.
Remove _start() and _stop() lifecycle states from the OS context.  We
won't need themm.
Generate initial device requests from block and char devices as reported
by sysfs, instead of triggerring uevents.  Add requisite logic for
parsing sysfs files and walking the relevant sysfs directories.
Add test back-end
Add vdev_read_uninterrupted(), and move group/passwd parsing methods to
util.cpp
Plumb through device request enqueuing to the workqueue methods that
add/remove them.
Example vdev.conf, vdev acl, and vdev action
Merge branch 'master' of https://github.com/jcnelson/loginfs