doc/go1.16: consolidate stdlib changes in "Minor changes" section
Many of the standard library changes that were added before CL 272871
ended up in the "Core library" section. That section is meant for
major changes like new packages, and most of these aren't.
Consolidate all changes in the "Minor changes to the library" section
for now, so that it's easier to get a complete picture of changes for
each package, along with the remaining TODOs. Add a TODO to read them
over at the end and factor out items that are worth highlighting.
Apply minor other fixups to improve consistency.
For #40700.
Change-Id: I7dc2e7ebf2ea3385fce0c207bae4ce467998a717
Reviewed-on: https://go-review.googlesource.com/c/go/+/273267
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org> Reviewed-by: Katie Hockman <katie@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>