Sort most attributes alphabetically
Minor changes to `rust.md`, and `guide-ffi.md`.

  * `rust.md`: whanges for consistency

  * `guide-ffi.md`: wrapped inline code
~ -> Box in the manual

Fixes #16439
libcore: rename private cmp macros

eq_impl! => partial_eq_impl!
totaleq_impl! => eq_impl!
ord_impl! => partial_ord_impl!
totalord_impl! => ord_impl!
Sort `Marker types` and add missing language items
auto merge of #16428 : mdinger/rust/sort_attributes, r=cmr

Targetting at fixing most of #16414.

Sorts these alphabetically:
* [Crate-only attributes](http://doc.rust-lang.org/rust.html#crate-only-attributes)
* [Function-only attributes](http://doc.rust-lang.org/rust.html#function-only-attributes)
* [Miscellaneous attributes](http://doc.rust-lang.org/rust.html#miscellaneous-attributes)
* [Lint check attributes](http://doc.rust-lang.org/rust.html#lint-check-attributes)
* [Built-in Traits](http://doc.rust-lang.org/rust.html#built-in-traits)
* [Types](http://doc.rust-lang.org/rust.html#types)
* [Deriving](http://doc.rust-lang.org/rust.html#deriving)
* [Compiler Features](http://doc.rust-lang.org/rust.html#compiler-features)

Doesn't modify these:
* [Operators](http://doc.rust-lang.org/rust.html#operators): An alternative sorting is unclear.
* [Marker types](http://doc.rust-lang.org/rust.html#marker-types): Could be sorted but uncertain how. See below.
* [Stability](http://doc.rust-lang.org/rust.html#stability): Already sorted by stability

---

[Marker types](http://doc.rust-lang.org/rust.html#marker-types) has an extra newline above `fail_` which may throw off formatting (see #16412) or it may be for some other reason. If the newline is just a typo, I can just remove it and format this alphabetically like so:
```rust
// Sorted alphabetically
a_bread
b_bread
c_bread
fail_
fail_bounds_check
a_type
b_type
c_type
```

Marker types is listed as likely to become out of date so I don't know if this is worth doing anyway.

[EDIT] modified `Marker types` now and tried to update the language items list.
auto merge of #16440 : bheesham/rust/master, r=brson

  * `rust.md`: changes for consistency

  * `guide-ffi.md`: wrapped inline code

NOTE: This is a duplicate of #16375. I completely messed up that fork, so I made a new fork.
auto merge of #16444 : steveklabnik/rust/fix_boxes_in_manual, r=brson

Fixes #16439
auto merge of #16470 : liigo/rust/rename-private-cmp-macros, r=brson

eq_impl! => partial_eq_impl!
totaleq_impl! => eq_impl!
ord_impl! => partial_ord_impl!
totalord_impl! => ord_impl!
debuginfo: Add a "no_debug" attribute that allows to exclude functions from debuginfo generation.