Squashed commit of the following:

commit 822a3ab7dfa2aa1ae22c03fe47c8e9dcf967afa5
Author: Damian Bogel <damian.bogel@gmail.com>
Date:   Sun Sep 8 13:07:33 2013 +0200

    fsd naming changes.
    Small fsd bugfix with hook instance data.
    fsh made invulnerable to {mount,free}, {mount,free} callback
    installation in {mount,free} callback. (previously caused a deadlock)

commit abb6419b7e155f60da2afe10abab3e2b37db0597
Author: Damian Bogel <damian.bogel@gmail.com>
Date:   Fri Sep 6 19:13:49 2013 +0200

    Eliminated recursive calls from hooks execution in fsh.
    Adjusted fsd code to this changes.
    Comments in fsh and fsd aren't yet adjusted to this changes.

commit 324fab3601451d44bb08669b20fe0da7c71ca104
Author: Damian Bogel <damian.bogel@gmail.com>
Date:   Wed Sep 4 11:40:14 2013 +0200

    Fixed unprotected fsd_enabled in fsd_ioctl() issue.

commit f7762820494aa2892bc583d2aaf0740d8ac14b59
Author: Damian Bogel <damian.bogel@gmail.com>
Date:   Tue Sep 3 17:19:09 2013 +0200

    Fixed fsd_detach.
    Deleted fsd_callback_free (it's unnecessary, becuase when vfs_t is
    being destroyed, hook remove callbacks are being fired).
Adjustments to new fsh (pre and post hooks)