net-libs/loudmouth: use official tarballs

net-libs/loudmouth: use official tarballs

Previously, Github-generated tarballs were used.

These required extra build step known as "bootstrapping", which required
eautoreconf run, and imposed a dependency on dev-util/gtk-doc (which I
worked around earlier rather inelegantly).

At the same time, this change has a side effect of disabling -Werror in
compilation flags, which is the reason of bug 673434.

Suggested-by: Mart Raudsepp <leio@gentoo.org>
Bug: https://bugs.gentoo.org/673434
Package-Manager: Portage-2.3.49, Repoman-2.3.12
Signed-off-by: Andrey Utkin <andrey_utkin@gentoo.org>