Group Build-Depends lines by purpose

Build tools, i18n tools, compression, security and UI libraries, and
perl packages for the test suite.

debian/control

@@ -9,10 +9,11 @@ Homepage: http://wiki.debian.org/Teams/Dpkg
 Vcs-Browser: http://git.debian.org/?p=dpkg/dpkg.git
 Vcs-Git: git://git.debian.org/git/dpkg/dpkg.git
 Standards-Version: 3.9.2
-Build-Depends: debhelper (>= 7), pkg-config,
+Build-Depends: debhelper (>= 7), pkg-config, flex,
  gettext (>= 0.18), po4a (>= 0.33.1),
- libncursesw5-dev, zlib1g-dev (>= 1:1.1.3-19.1), libbz2-dev, flex,
+ zlib1g-dev (>= 1:1.1.3-19.1), libbz2-dev,
  libselinux1-dev (>= 1.28-4) [linux-any],
+ libncursesw5-dev,
  libtimedate-perl, libio-string-perl
 
 Package: libdpkg-dev