Install localized man pages from debian/rules

Currently dh_installman does not handle distinct man pages depending on
the full path, it only uses the filename, so the last match wins, which
makes installation of localized man pages to be overridden by the
original version, being that the last one listed.

Move the localized man pages installation to debian/rules, which avoids
a possible debhelper Build-Depends version bump (in case it was made to
support such cases); but most important, it reduces duplication because
the list of localized man pages is based on the original man pages list
found in the .manpages debhelper config files.

Regression introduced in commit d7c001aa

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Spotted-by: Raphaël Hertzog <hertzog@debian.org>