Packaging cleanup

* Declare compliance with policy 4.5.1
* Bump debhelper compat level to 13
* Update debian/watch to version 4

debian/control

@@ -1,10 +1,10 @@
 Source: ngircd
 Maintainer: Christoph Biedl <debian.axhn@manchmal.in-ulm.de>
 Homepage: https://ngircd.barton.de/
-Standards-Version: 4.4.1
+Standards-Version: 4.5.1
 Vcs-Browser: https://git.in-ulm.de/cbiedl/ngircd
 Vcs-Git: https://git.in-ulm.de/cbiedl/ngircd.git
-Build-Depends: debhelper-compat (= 12),
+Build-Depends: debhelper-compat (= 13),
     expect,
     libgnutls28-dev,
     libident-dev,

debian/watch

@@ -1,4 +1,4 @@
 
-version=3
+version=4
 opts=pgpsigurlmangle=s/$/.sig/ \
-    https://arthur.barton.de/pub/ngircd/ngircd-([0-9\.]+)\.tar\.xz
+    https://arthur.barton.de/pub/@PACKAGE@/@PACKAGE@-([0-9\.]+)@ARCHIVE_EXT@