Unionfs: imported fixes from korg branch's take-3 series

Unionfs: imported fixes from korg branch's take-3 series

- removed EACCES/EROFS text from issues.txt
- updated sioq.[hc] copyright dates to 2006 (not earlier)
- added small XXX comment to xattr copyup code (selinux CAP_FOWNER stuff) to
  say that entire copyup code should be moved to SIOQ.
- copyup_xattr: renamed name_list_orig -> name_list_buf
- multi-line static inline unionfs_xattr_kfree
- rewrote unionfs_interpose a bit cleaner (no backward goto's, better
  variable names, use small util fxn, etc.)
- introduced CONFIG_UNION_FS_DEBUG instead of hand-editing makefile
- unionfs_mntget/put cleanups
- bug fix to is_robranch_idx (thanks to Patrick Aussems).  Fixed bug #571.
- fixed a couple of important bugs in our init/release_lower_nd

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>