The only non-obvious changes:
- `building/storage_live_dead_in_statics.rs` has a `#[rustfmt::skip]`
attribute to avoid reformating a table of data.
- Two `.mir` files have slight changes involving line numbers.
- In `unusual_item_types.rs` an `EMIT_MIR` annotation is moved to
outside a function, which is the usual spot, because `tidy` complains
if such a comment is indented.
The commit also tweaks the comments in `rustfmt.toml`.
It makes it sound like the `ExprKind` and `Rvalue` are supposed to represent all pointer related
casts, when in reality their just used to share a some enum variants. Make it clear there these
are only coercion to make it clear why only some pointer related "casts" are in the enum.
