Various debian fixes (squashed commit)

- Bump standards version to 3.9.5 (no changes).
- Remove obsolete DM-Upload-Allowed header.
- Build with dpkg-flags, for hardening.
- Force re-building of user guide on Debian.
- Don't ignore failure of invoke-rc.d; fixes lintian warning.
- Use my Debian e-mail address in Uploaders.
- Pass dpkg-buildflags to actual configure command.
- Allow LDFLAGS to be provided in the environment and consistently use
  $(LDFLAGS) when linking (not partially linking).
- Remove funny 'Non-maintainer upload' line, fix version.
One small comment correction while "merging" stuff.
Pass generate.consistent.ids flag to xsltproc so id tags in HTML output will
no longer be randomised, so when you generate the file from the same input,
it will in fact generate the same output.
Support building against libgnutls28-dev. Closes: #753020
Add missing dependency of install-systemd on systemd.
Fix word_wrap memory leak...