Packaging cleanup

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

debian/control

@@ -1,11 +1,11 @@
 Source: file
 Maintainer: Christoph Biedl <debian.axhn@manchmal.in-ulm.de>
 Homepage: https://www.darwinsys.com/file/
-Standards-Version: 4.4.1
+Standards-Version: 4.5.1
 Vcs-Browser: https://git.in-ulm.de/cbiedl/file
 Vcs-Git: https://git.in-ulm.de/cbiedl/file.git
 Testsuite: autopkgtest
-Build-Depends: debhelper-compat (= 12),
+Build-Depends: debhelper-compat (= 13),
     libbz2-dev,
     liblzma-dev,
     zlib1g-dev,

debian/libmagic-dev.install

@@ -1,5 +1,5 @@
 usr/include
 usr/lib/*/*.a
 usr/lib/*/*.so
-usr/share/man/man3
 usr/lib/*/pkgconfig/libmagic.pc
+usr/share/man/man3

debian/watch

@@ -1,4 +1,4 @@
 
-version=3
+version=4
 opts=pgpsigurlmangle=s/$/.asc/ \
-    ftp://ftp.astron.com/pub/file/file-(.*?)\.tar\.gz
+    ftp://ftp.astron.com/pub/@PACKAGE@/@PACKAGE@-@ANY_VERSION@@ARCHIVE_EXT@