debian: Use dh_autoreconf.

Use dh_autoreconf instead of invoking autogen.sh in the configure
target.

debian/control

@@ -7,7 +7,7 @@ Build-Depends: debhelper (>= 9), automake (>= 1:1.12), gettext,
  libfontconfig1-dev, libjpeg-dev, libpng-dev, libsm-dev, libtiff5-dev,
  libtool, libgif-dev, libx11-dev, libxext-dev, libxft-dev, libxinerama-dev,
  libxkbfile-dev, libxpm-dev, libxt-dev, libxrender-dev, sharutils, libxmu-dev,
- libxrandr-dev, dctrl-tools, autotools-dev
+ libxrandr-dev, dctrl-tools, dh-autoreconf
 Homepage: http://windowmaker.org/
 
 Package: wmaker