debian/control: Update Standards-Version
debian/rules: Add '--with autotools-dev' to debhelper

Add autotools-dev to update config.{sub,guess} and {libtool,aclocal}.m4
during build time.

Closes: #727287
Thanks: Mattias Klose
debian/control: Update Vcs locations
debian/compat: Update debhelper compat to v9
debian/libesmtp6.postinst: Remove unnecessary postinst script