* Update call to sphinx-autobuild (remove --poll -B options, add --open-browser)
* Upgrade the Sphinx and sphinx-tabs versions.
* utils/makefile.sphinx: remove the SPHINXVERS variable.
* utils/makefile.sphinx: remove the sphinx-doc and sphinx-live targets, Sphinx is already installed by the pyenvinstall target.
The sphinx-doc-prebuilds is the single point of definition for prerequisites
each doc build needs
BTW: remove $(LXC_ENV_FOLDER) offset from BOOKS_FOLDER and DOCS_FOLDER path.
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>