Do not call update-mime in maintainer scripts

See merge request debian/debianutils!2

There has been a trigger for that since mime-support 3.52-1, released
in February 2012.

Dmitry Bogatov authored Aug 17, 2019 and Clint Adams committed Sep 06, 2019

Closes: #719692

Use mkstemps(3) instead of tempnam(3).

See merge request debian/debianutils!1

tempnam(3) is insecure, not recommended to be used, marked as obsolete
in POSIX.1-2008. In fact, pseudo(1) fakeroot replacement for
OpenEmbedded, blocks the use of tempnam(3) and tmpnam(3) hardcoding
them to return ENOMEM.

Reimplement tempfile using mkstemps(3), performing directory selection
according to tempfile's manual page.

Update the manpage accordingly.

Andreas Henriksson authored Mar 24, 2016 and Clint Adams committed Jun 29, 2016

In the case of usr merged systems we want the shells to also
be listed with their real paths, eg. /usr/bin/bash, in addition
to their specified path in /etc/shells

(While at it also fix mixed tab/spaces indentation of help texts
and trailing whitespace.)

The mixture of dirname/realpath/basename is to avoid expanding
the filename, only the directory part of the path.
This is to avoid /bin/sh being expanded to /usr/bin/dash
rather than /usr/bin/sh. Maybe we want to add both in
such a case?

Closes: #817168