tar: work aruond IBM XL C bug

* src/incremen.c (show_snapshot_field_ranges)
(write_directory_file_entry): Use simpler array size expression,
one that evaluates to the same value.  This works around a compiler
bug with IBM XL C.  Problem reported by Yannick Bergeron in
<http://lists.gnu.org/archive/html/bug-tar/2014-01/msg00009.html>.
Minor bugfixes

* src/compare.c (diff_dumpdir): Close descriptor if fstat failed.
(diff_multivol): Make sure the descriptor is closed and eventual
errors reported if lseek fails.
Both reported by Jiri Kukacka.
Fix the use of --no-recursion and --recursion options.

Each option remains in effect until cancelled by the next ocurrence
of its counterpart, as stated in the documentation.

* src/names.c (name_next_elt): Restore recursion_option from the
value of matching_flags.