- change a lot of occurances of errno to use strerror(errno). We can't

- change a lot of occurances of errno to use strerror(errno). We can't
assume all our users are programmers :-)

- automatically create the smbpasswd file if it doesn't exist when
running smbpasswd.
(This used to be commit 1d2361bd2dec35bce029699f54c6a61fa739fa4b)