* Use "the syntax of" uniformly.
* Use asterisks for all defined terms.
* Define more terms, espcially in the syntax section.
** Reword things so that definitions are generally first.
** I did not necessarily go with the best wording; the idea is to
   improve, not perfect. I still need to dedicate time to each
   expressions individually.
* Remove usage of "the compiler" and "Rust".
** This also involved rewording.
** How to deal with closure types and closure expressions is gonna be
   an interesting question to solve. I avoided solving it here.
* Remove non-normative information or put them in a `Note`.
* A few added section headers
* Move links to the bottom

Note that I've left quite a few nonsensical statements alone, such as
any that use "denote". They'll be treated separately.

About halfway through the list of expressions and this PR is getting
large. So I'm gonna cut this one here, stopping at grouped expressions
in the alphabetical list.

Co-authored-by: Eric Huss <eric@huss.org>

* Go back to calling the syntactic elements "expressions", but name
  them operands afterwards.
* Use "called XYZ" to name something in syntax.
* Trade out a few uses of expressions using letters for operand names
  for the actual operand names.
* Pick arbitrary names for the operands. I don't like some of them, but
  they're not set in stone.
* Say they're not set in stone in the main expressions chapter.

Co-authored-by: Eric Huss <eric@huss.org>