I started tweaking this patch, and wound up going through the whole doc and fixing the references to 'byte string' and 'string' throughout, as well as making all the entries consistent in how they reference the function arguments and output (previously some did not reference the output at all, nor was it clear that the output is always bytes).  I believe I also clarified some confusing wordings along the way.

Since there are so many changes I need some eyes checking my work before I commit.

Note that the primary motivation for this change (the incorrect claim that both interfaces supported the RFC) is not made by the 2.7 docs, and since those docs are very different now, I don't plan to touch them.