devel/liblogging: update to 1.0.7

It's been 3 months since 1.0.7 was tagged on GitHub, but there's been
no release tarball made available at
http://download.rsyslog.com/liblogging/. Therefore, switch to GitHub
as the download site.

Add USE=autoreconf and BUILD_DEPENDS on textproc/py-docutils (for
rst2man) in order to generate the missing configure.sh and man pages,
which aren't included in the GitHub repository. Add USES=python:env
to access ${PY_FLAVOR}.

Changes: https://github.com/rsyslog/liblogging/blob/v1.0.7/ChangeLog
Reported by: repology