Build dependencies

Quite a list, still it's not comprehensive.

sudo apt-get install fakeroot debhelper dpatch libcap-dev pkg-config \
libspandsp-dev libssl-dev libsndfile1-dev libpq-dev libmysqlclient15-dev \
libspeex-dev libcurl3-dev unixodbc-dev libcapi20-dev zaptel-source \
libreadline-dev autoconf automake sox doxygen libtool