textual: fix the example in whereis man page, plus further improvements

Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
mount: remove ext4 journal=update from man page

It's already unsupported.

References: http://patchwork.ozlabs.org/patch/123291/
Reported-by: Roman Žilka <roman.zilka@gmail.com>
Signed-off-by: Karel Zak <kzak@redhat.com>
fstrim: remove unnecessary "were" from verbose message

Signed-off-by: Karel Zak <kzak@redhat.com>