Update MSVC_VERSION usage and table

[mwichmann]

Also convert usage of the term Microsoft Visual C++ (which was used in several forms, with/without "Microsoft", as C/C++, etc.) into an entity &MSVC; for consistency.

This is a doc-only change.

• [ ] I have created a new test or updated the unit tests to cover the new/changed functionality.
• [X] I have updated CHANGES.txt (and read the README.rst)
• [X] I have updated the appropriate documentation