man: do not ignore the exit status of roff tools

[wosch]

Summary

This will fix https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=223516

Test Plan

cat /dev/null > /tmp/bla.1.gz
man /tmp/bla.1.gz >/dev/null; echo $?

gzcat: /tmp/bla.1.gz: unexpected end of file
gzcat: /tmp/bla.1.gz: unexpected end of file
grotty:<standard input>:(<standard input>):6: fatal error: 'V' command invalid before first 'p' command
1

[emaste]

OK. Discarding errors from $cattool is not directly related to the original issue, right?

[wosch]

In D44798#1021008, @emaste wrote:

OK. Discarding errors from $cattool is not directly related to the original issue, right?

gzip may print (a useless) error message for large files if we catch SIGPIPE. E.g.

small input
(set -o pipefail; trap '' SIGPIPE; man cat | gzip |gzip -dc | head -1 >/dev/null; echo $?)
0

large input for gzcat
(set -o pipefail; trap '' SIGPIPE; man tcsh | gzip |gzip -dc | head -1 >/dev/null; echo $?)
gzcat: error writing to output: Broken pipe
gzcat: /usr/share/man/man1/tcsh.1.gz: uncompress failed
gzip: error writing to output: Broken pipe
1

You don't want to bother users with this new warnings.