Guide Redux: Pointers
Emit lifetime end markers in unwinding codepaths

Currently we don't emit lifetime end markers when translating the
unwinding code. I omitted that when I added the support for lifetime
intrinsics, because I initially made the mistake of just returning true
in clean_on_unwind(). That caused almost all calls to be translated as
invokes, leading to quite awful results.

To correctly emit the lifetime end markers, we must differentiate
between cleanup that requires unwinding and such cleanup that just wants
to emit code during unwinding.
rustdoc: Add a --target flag

Closes #13893
rustdoc: Hide impls for #[doc(hidden)] traits

Closes #14585
rustdoc: Bind keydown instead of keypress for nav

Apparently keypress doesn't quite work in all browsers due to some not invoking
the handler and jquery not setting the right `which` field in all circumstances.
According to http://stackoverflow.com/questions/2166771 switching over to
`keydown` works and it appears to do the trick. Tested in Safari, Firefox, and
Chrome.

Closes #15011
rustdoc: Fix inlining type parameters

I'm not entirely sure if the correct space can be inferred when cleaning
Generics, so the impl has been switched to take the space explicitly.

Closes #15099
rustdoc: Fix links to Box/Gc

These are lang items now, so the internal representations need to be
re-translated back to the original structures manually.

Closes #15185
Closes #15800
rustdoc: Correctly handle local renamings

Previously a `pub use` would not rename the destination in rustdoc, it would
always use the destination ident instead of the renamed ident.
rustdoc: Inline items from foreign mods

These were all just previously skipped.

Closes #15648
auto merge of #15789 : steveklabnik/rust/guide_pointers, r=cmr

This is super, super WIP, but I'm going to go get lunch for a while, and figured I'd toss my work up here in case anyone wants to see my work as I do it.

This contains a new introductory section explaining the basics of pointers, and some pitfalls that Rust attempts to solve. I'd be interested in hearing how my explanation is, as well as if this belongs here. Pointers are such a crucial concept, I don't mind having a beginners' section on them in the main docs, even though our main audience is supposed to understand them already. Reasonable people may disagree, however.
auto merge of #15975 : dotdash/rust/unwind_lifetimes, r=pcwalton

Currently we don't emit lifetime end markers when translating the
unwinding code. I omitted that when I added the support for lifetime
intrinsics, because I initially made the mistake of just returning true
in clean_on_unwind(). That caused almost all calls to be translated as
invokes, leading to quite awful results.

To correctly emit the lifetime end markers, we must differentiate
between cleanup that requires unwinding and such cleanup that just wants
to emit code during unwinding.
auto merge of #15982 : alexcrichton/rust/rustdoc-fixes, r=brson

Sadly there's still a lot of open issues, but this tackles some of the more pressing ones. Each commit has its own description along with the issues it closes.
Refactored syntax::fold.

Prior to this, the code there had a few issues:

- Default implementations inconsistenly either had the prefix `noop_` or
  not.
- Some default methods where implemented in terms of a public noop function
  for user code to call, others where implemented directly on the trait
  and did not allow users of the trait to reuse the code.
- Some of the default implementations where private, and thus not reusable
  for other implementors.
- There where some bugs where default implemntations called other default
  implementations directly, rather than to the underlying Folder, with the
  result of some ast nodes never being visted even if the user implemented that
  method. (For example, the current Folder never folded struct fields)

This commit solves this situation somewhat radically by making _all_
`fold_...` functions in the module into Folder methods, and implementing
them all in terms of public `noop_...` functions for other implementors to
call out to.

Some public functions had to be renamed to fit the new system, so this is a
breaking change.

[breaking-change]
Add a few more derivings to ast types