Improve error messages for vipw

[fernape]

Summary

This comes from PR 40572
In current, right now:

# EDITOR=false vipw
vipw: pw_edit(): No such file or directory

which doesn't seem too user friendly.

Adding des as reviewer since he seems to know the code pretty well according
to the svn log.

Test Plan

Test case 1:

# export EDITOR=false
# vipw
'false' failed with error code 1: Operation not permitted
vipw: no changes made

Teste case 2:

# export EDITOR=/home/test/idontexist
# vipw
'/home/test/idontexist' failed with error code 2: No such file or directory
vipw: no changes made

Test case 3:

# export EDITOR=vim
# vipw
(I write the file)
vipw: password list updated

Test case 4:

# export EDITOR=vim
# vipw
(I do not write the file)
vipw: no changes made

[bcr]

Typo fix in comment.

lib/libutil/pw_util.c

362

s/acces/access/

[fernape]

Fix typo in comment reported by bcr@

[tcberner]

I think as this is not in ports/ I cannot contribute much here :D

[fernape]

In D14887#320410, @tcberner wrote:

I think as this is not in ports/ I cannot contribute much here :D

OK. Let's see if someone with commit in base has a look :)

[fernape]

A version of this has been committed in https://svnweb.freebsd.org/changeset/base/362430