option/result overviews: address feedback

(Most of these are from a review by joshtriplett. Thanks!)

Fix errors in `as_pin_ref` and `as_pin_mut` in the "Adapters for
working with references" overview.

Reword some headings about transformation methods.

Reclassify `map`, `map_or`, `map_or_else`, `map_err`, etc. to more
accurately reflect which variants they transform.

Document `Debug` requirement for `get_or_insert_default`.

Reword text about `take` and `replace` to be more accurate.

Add examples for the `Product` and `Sum` traits.

Also:

Move link reference definitions closer to their uses. Warn about making
link reference definintions for `err` and `ok`. Avoid making other link
reference definitions that might conflict in the future (foreign methods
that share a name with local ones, etc.)

Write out the generics of `Option` and `Result` when the following
text refers to the type parameters.

0 files changed, 0 insertions, 0 deletions