Try newer version of Sphinx.

Update ODPI-C and tweak release notes in preparation for release of

cx_Oracle 8.2.1.

Configuration requires master_doc (root_doc in Sphinx 4.0).

Tweak top-level description for Oracle Client library and Python support

levels.

Further tweaks to documentation and release notes in preparation for …

…release

of 8.0.1.

Update to ODPI-C 4.0.1 and add test to ensure that the offset is retu…

…rned

correctly when a parse error is encountered.

Explicitly mention Python 3.8 support.

Preparing to release cx_Oracle 7.2.3.

Preparing to release cx_Oracle 7.2.2.

Preparing to release cx_Oracle 7.2.1.