debian: Switch to debhelper 10

debhelper 10 is much nicer with the installation part from
a dirty tree, so you can just fix some stuff breaking the
install step and then continue building with debuild -b -nc
until you have fixed all your stuff.

It also has some other advantages, of course, like some
bug fixes in shell escaping for maintscript, or systemd
helper changes.

debian/compat

@@ -1 +1 @@
-9
+10

debian/control

@@ -6,7 +6,7 @@ Uploaders: Michael Vogt <mvo@debian.org>,
  Julian Andres Klode <jak@debian.org>,
  David Kalnischkies <donkult@debian.org>
 Standards-Version: 3.9.8
-Build-Depends: dpkg-dev (>= 1.17.14), debhelper (>= 9.20141010), libdb-dev,
+Build-Depends: dpkg-dev (>= 1.17.14), debhelper (>= 9.20160709~), libdb-dev,
  gettext (>= 0.12), libcurl4-gnutls-dev (>= 7.19.4~),
  zlib1g-dev, libbz2-dev, liblzma-dev, liblz4-dev (>= 0.0~r126),
  xsltproc, docbook-xsl, docbook-xml, po4a (>= 0.34-2),

debian/rules

@@ -11,7 +11,7 @@ export DPKG_GENSYMBOLS_CHECK_LEVEL=0
 export CTEST_OUTPUT_ON_FAILURE=1
 
 %:
-	dh $@ --with systemd --parallel --buildsystem=cmake
+	dh $@
 
 override_dh_install-indep:
 	dh_movefiles