debian/compat: upgrade to compat level 9

- enable hardening

- fix dh syntax. Now that we have compat level 9, the old, wrong
  syntax is no longer accepted.

- update debian/libnotmuch{3,-dev}.install for multiarch.

- update versioned dependency on debhelper.

debian/compat

@@ -1 +1 @@
-7
+9

debian/control

@@ -7,7 +7,7 @@ Uploaders:
  martin f. krafft <madduck@debian.org>,
  David Bremner <bremner@debian.org>
 Build-Depends:
- debhelper (>= 7.0.50~),
+ debhelper (>= 9),
  pkg-config,
  libxapian-dev,
  libgmime-2.6-dev (>= 2.6.7~) | libgmime-2.4-dev,
@@ -39,6 +39,7 @@ Package: libnotmuch3
 Section: libs
 Architecture: any
 Depends: ${shlibs:Depends}, ${misc:Depends}
+Pre-Depends: ${misc:Pre-Depends}
 Description: thread-based email index, search and tagging (runtime)
  Notmuch is a system for indexing, searching, reading, and tagging
  large collections of email messages in maildir or mh format. It uses

debian/libnotmuch-dev.install

@@ -1,2 +1,2 @@
 usr/include
-usr/lib/libnotmuch.so
+usr/lib/*/libnotmuch.so

debian/libnotmuch3.install

@@ -1 +1 @@
-usr/lib/libnotmuch.so.*
+usr/lib/*/libnotmuch.so.*

debian/rules

@@ -1,7 +1,7 @@
 #!/usr/bin/make -f
 
 %:
-	dh --with python2 $@
+	dh $@ --with python2
 
 override_dh_auto_configure:
 	dh_auto_configure -- --emacslispdir=/usr/share/emacs/site-lisp/notmuch