debhelper updates

* Use debhelper compat level v7 when building packages. All changes
  since v4 seem safe for alien's generated rules files.
* Use dh_prep instead of deprecated dh_clean -k.

Alien/Package/Deb.pm

@@ -383,6 +383,11 @@ sub prep {
 		close OUT;
 	}
 
+	# Use debhelper v7
+	open (OUT, ">$dir/debian/compat") || die "$dir/debian/compat: $!";
+	print OUT "7\n";
+	close OUT;
+
 	# A minimal rules file.
 	open (OUT, ">$dir/debian/rules") || die "$dir/debian/rules: $!";
 	my $fixpermscomment = $this->fixperms ? "" : "#";
@@ -390,12 +395,6 @@ sub prep {
 #!/usr/bin/make -f
 # debian/rules for alien
 
-# Uncomment this to turn on verbose mode.
-#export DH_VERBOSE=1
-
-# Use v4 compatability mode, so ldconfig gets added to maint scripts.
-export DH_COMPAT=4
-
 PACKAGE=\$(shell dh_listpackages)
 
 build:
@@ -411,7 +410,7 @@ binary-indep: build
 binary-arch: build
 	dh_testdir
 	dh_testroot
-	dh_clean -k -d
+	dh_prep
 	dh_installdirs
 
 	dh_installdocs