Documentation: Wholesale update of sphinx config/scripts

Newer versions of Sphinx (espescially v3.0+) break compatibility quite
severely against older kernel versions such as this. There are a very
large number of changes needed to get even rudimentary compilation
working again.

Instead of manually cherry-picking all of the changes, update just the
sphinx configs and scripts by copying the respective files from the
latest upstream version. There'll still be a fairly sizeable number of
warnings and errors with sufficiently new sphinx versions, but at least
it'll build. (The KUnit pages seem to come out okay, at least).

Change-Id: I7077c30695e14a72a4d5570cd8412dcf9cd60bb3
14 files changed