ownership_check: Tune to allow bin (compatibility for old packages)

Signed-off-by: David Spencer <baildon.research@googlemail.com>
architecture_check: Fix error (explanation not displayed).

Signed-off-by: David Spencer <baildon.research@googlemail.com>
info_check: Add new checks, tune existing check.

Add check for 'dir' file, which should not be present.
Add check for install-info command in doinst.sh.
Tune uncompressed info page check with regex (reduce false +ves).

Signed-off-by: David Spencer <baildon.research@googlemail.com>
Add whitelist (see --exclude-from) for Slackware.

Signed-off-by: David Spencer <baildon.research@googlemail.com>