doc: Correctly onclose code blocks in HashSet
Remove an unneeded FIXME in coherence.rs

Also, let f; f = ...; is just wrong.
doc: TreeSet methods and main example.
doc: TreeMap methods with examples.

Small corrections for TreeSet examples.
doc: Main example for TreeMap.
Hash the length of the RingBuf before hashing elements
auto merge of #16030 : treeman/rust/doc-hashset-fix, r=sfackler

Not sure how this could slip by.
doc: Small rewording.
Implement Hash for tuples of up to arity 12. Also change the style to be consistent with core::tuple
Make test expansion induce less reachability

We previously reexported entire modules, which caused private things to
become reachable and trip the dead code and private items in public API
lints.

Closes #15912
auto merge of #16020 : nham/rust/ringbuf_hash_ord, r=alexcrichton

cc #15294
auto merge of #16026 : ruud-v-a/rust/patch-1, r=steveklabnik
auto merge of #16031 : arielb1/rust/remove_unneeded_fixme, r=kballard

The issue was fixed a month ago - remove the workaround.
Implement PartialOrd for TrieMap and TrieSet
Implement PartialOrd for SmallIntMap
Implement PartialOrd for Bitv and BitvSet
Implement Ord for TrieMap/TrieSet/SmallIntMap/Bitv/BitvSet
rustdoc: show struct field docs when inlined

Some minor changes to the compiler to expose this information. Very
inconvenient since struct fields aren't an item. Adds (yet another) table to
metadata.

Closes #15739
rustdoc: remove extraneous .move_iter().collect()s

The impl of Clean for Vec obsoleted these long, long ago.
rustc: encode is_sugared_doc on ast::Attribute