Bug 27315: use the namespace-aware docbook stylesheet

Bug 27315: use the namespace-aware docbook stylesheet

When viewing the man page for the `koha-list` command, the output does
not appear correctly: there appears to be a "staircase"-like effect on
the text. The same is true for all other man pages.

The source XML files for our man pages have the following namespace
declaration at the top: xmlns='http://docbook.org/ns/docbook', which
means they are DocBook V5.0 documents and should be processed by
namespace-aware DocBook XSL stylesheets.

This patch fixes that by using the DocBook-to-man-page transformation
stylesheet from the docbook-xsl-ns package (note the "-ns" suffix).

Test plan:
1) Apply the patch
2) Build and install new package
3) Confirm the man pages display correctly

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>