debugfs: create journal handling routines

debugfs: create journal handling routines

Create a journal.c with routines adapted from e2fsck/journal.c to
handle opening and closing the journal, and setting up the
descriptors, and all that.  Unlike e2fsck's versions which try to
identify and fix problems, the routines here have no way to repair
anything.

[ Modified by tytso to fold debugfs/jfs_user.h into e2fsck/jfs_user.h,
  so we don't have to copy recovery.c and revoke.c into debugfs. --tytso ]

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>