Be more clear about what this lambda expression does
Give more explanation when introducing closures
Demonstrate accessing external variable in first example
Some more closure changes
Fix typo
Remove extra semicolons
Suggested revisions to PR 13676.

Most important: distinguish function decl sugar for omitting `-> ()`
from type inference on closures.  I also tried to add a couple more
examples to further emphasize this distinction.  Note that this sugar
(of omitting `-> ()`) is actually already briefly mentioned in an
earlier section, so it is a little tricky deciding whether to put more
material here, or to move it up to the previous section.

Other drive-by fixes:

 * Fix the line length of the code blocks to fit in the width provided
   in the rendered HTML

 * Some minor revisions to wording (e.g. try to clarify in some cases
   where a type mismatch is arising).
Allow manual implementations of built-in traits

[RFC #3]

cc #13231
Merge pull request #1 from pnkfelix/clarify-omit-unit-vs-inference

Suggested revisions to PR 13676.
Add more comprehensive unit tests for SIMD binops
BigUint always use u64 as the internal machine unsigned integer

This change allow a speedup of ~1.5 on shootout-pidigits on a i32
system.  `DoubleBigDigit` is used to abstract the internal
unsigned integer used in computation to simplity future
architecture specialization.

`BigDigit::from_uint` and `BigDigit::to_uint` become
`BigDigit::from_doublebigdigit` and `BigDigit::to_doublebigdigit`.

[breaking-change]
Allow built-in traits to be derived

[RFC #3]

cc #13231
Implement ToJson for Vec<T>

Now that ~[T] is obsolete, we need to allow to_json() to work for
vectors.
rustdoc: escape shown input to prevent injection
Implement comparison operators for int and uint SIMD vectors
rustc: Use the "real" realpath function

The logic of the custom realpath function in metadata::loader was incorrect, but
the logic in util::fs was correct.

Closes #13890
Provide a note if method lookup fails and there are static definitions with the same name.
Add lint check for negating uint literals and variables.

See #11273 and #13318
rustc: Crawl static initializers for reachability

This ensures that private functions exported through static initializers will
actually end up being public in the object file (so other objects can continue
to reference the function).

Closes #13620
auto merge of #13579 : hirschenberger/rust/lint_unsigned_negate, r=alexcrichton

See #11273 and #13318