Guide Redux: Pointers
Fill in example code for HashMap.

Add an example showing how to use the map with a custom type. Fill in
examples for methods in the hashmap file without ones.

Also move pop_equiv next to related public methods, to not create a
duplicate trait implementation in the docs.
Remove explicit rust code specifier. Unhide use HashMap.
Documentation examples for LruCache.
Cleanup LruCache doc.
Cleanup HashMap documentation.

Link to mentioned methods. Use `# Failure` tags to describe failure.
Make `pop_equiv`, `find_equiv` and `get_copy` standalone.
Fix display of `-NaN%` in borrock stats caused by div by zero
Add methods for obtaining iterators over the keys and values of a TreeMap
mk: Add check-secondary target for tests with no x-platform risk.

We'll use this to run a subset of the test suite onto a dedicated
bot.

This puts the grammar tests and the pretty-printer tests under
check-secondary. It leanves the pretty tests under plain `check`
for now, until the new bot is added to take over.

Because check-secondary is not run as part of `make check` there
will be a set of tests that most users never run and are only
checked by bors. I think this will be ok because grammar tests
should rarely regress, and the people regressing such tests
should have the fortitude to deal with it.
mk: Add comments to primary check targets
mk: Some fixes to grammar.mk

Invoke rustc in a way that sets LD_LIBRARY_PATH,
and disable the deps on RustLexer.class when antlr isn't available.
Add methods for obtaining iterators over the keys and values of a SmallIntMap
Add methods for obtaining iterators over the keys and values of a TrieMap
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
Fix assert message
rustdoc: Hide impls for #[doc(hidden)] traits

Closes #14585
auto merge of #15958 : hirschenberger/rust/borrock-stats-div-by-zero, r=alexcrichton

`rustc -Z borrowck-stats` displays ugly `-NaN%` in the stats

```
paths requiring guarantees: 0
paths requiring loans     : 0 (-NaN%)
paths requiring imm loans : 0 (-NaN%)
stable paths              : 0 (-NaN%)
```
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