Fix bug with "seq 10.8 0.1 10.95", plus another bug with %% in format.

Fix bug with "seq 10.8 0.1 10.95", plus another bug with %% in format.

* NEWS: Mention the %%-in-format bug fix.
* src/seq.c (struct layout): New type.
(long_double_format): New arg LAYOUT.  Fill it in.  Fix mishandling
of %% in formats.
(print_numbers): New arg LAYOUT.  Don't convert LAST to output format
when deciding whether to go slightly past LAST.  Instead, convert
X to output format and back.  This fixes a bug reported by
Andreas Schwab in
<http://lists.gnu.org/archive/html/bug-coreutils/2007-10/msg00237.html>
where "seq 10.8 0.1 10.95" would output 11.0 on platforms where
10.95 rounds to a value that prints as 11.0 when only one digit
past the decimal point is asked for.
(main): Compute layout, for benefit of print_numbers.
* tests/misc/seq (float-3): Undo previous change, since the bug
should be fixed now.
(fmt-b): New test, for the %% bug.