Ignore -N in "gzip -dN <in.gz" and "zcat -N in.gz"

Ignore -N in "gzip -dN <in.gz" and "zcat -N in.gz"

Have -c override -N, like other gzip implementations.  Before, our -N
(decompress to stored name) overrode -c (cat to stdout) and crashed
with a pledge violation, because the pledge for -c excludes wpath.

Guilherme Janczak reported the pledge violation in July 2022 and
provided a diff to prevent it, along with a regress test.  I rewrote
the diff and expanded the regress.

ok kn@ millert@