Imported gitlog-to-changelog from gnulib

This will be used to generate ChangeLog, which is recommended by GNU.
Added gitlog-to-{authors,news}

These will be used to generate, respectively, the AUTHORS and NEWS files that
are a part of GNU distributions.
Now using automake and autoconf

This implements recommendations by Brandon Invergo for the GNU submission
process, some of which is required by the GNU Coding Standards; I thank him for
his help and swift responses during this time.