Improved the search by including a levenshtein distance calculation which enables the docs search function to be more forgiving for spelling mistakes
Updated the licensing information for the Levenshtein distance function
Documentation examples for LruCache.
Cleanup LruCache doc.
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.
Make most of the failure functions take &(&'static str, uint)

Passing one pointer takes less code than one pointer and an integer.
Put the struct passed to unwinding functions into a static

Produces very clean asm, but makes bigger binaries.
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
rustc: Future proof runtime injection

Rename and gensym the runtime on import, so that users
can't refer to the `native` crate.

This is unlikely to break code, but users should import the "native" crate directly.

[breaking-change]
mk: Remove check-syntax target

This appears to be redundantly named with a shortcut target for
testing the syntax crate.
mk: Print grammar info message like others