debian: compress package with xz

All currently supported distros support this format.

debian/changelog

+i2p (0.9.7-3) UNRELEASED; urgency=low
+
+  * debian/rules: compress with xz
+
+ -- Kill Your TV <killyourtv@i2pmail.org>  Thu, 01 Aug 2013 23:26:52 +0000
+
 i2p (0.9.7-2) unstable; urgency=low
 
   * Bugfix: Add missing ; to i2prouter script.

debian/rules

@@ -106,7 +106,7 @@ override_dh_dhlibdeps:
 #	dh_installinit -r
 
 override_dh_builddeb:
-	dh_builddeb -- -Zbzip2
+	dh_builddeb -- -Zxz
 
 get-orig-source:
 	uscan --verbose --rename --destdir $(CURDIR)/.. --watchfile debian/watch --force-download