Packaging cleanup

* Declare compliance with policy 4.4.0
* Bump to debhelper compat level 12

debian/compat

@@ -1 +0,0 @@
-10

debian/control

@@ -1,10 +1,10 @@
 Source: http-parser
 Maintainer: Christoph Biedl <debian.axhn@manchmal.in-ulm.de>
 Homepage: https://github.com/joyent/http-parser
-Standards-Version: 4.1.1
+Standards-Version: 4.4.0
 Vcs-Browser: https://git.in-ulm.de/cbiedl/http-parser
 Vcs-Git: https://git.in-ulm.de/cbiedl/http-parser.git
-Build-Depends: debhelper (>= 10~),
+Build-Depends: debhelper-compat (= 12),
 Priority: optional
 Section: libs