mandelbrot: fix overlapping buffers
debuginfo: Don't crash when encountering global variable with unknown source span.
stability lint: ignore code from macro expansion

This small patch causes the stability lint to bail out when traversing
any AST produced via a macro expansion. Ultimately, we would like to
lint the contents of the macro at the place where the macro is defined,
but regardless we should not be linting it at the use site.

Closes #15703
btree: use pattern matching instead of unwrap
syntax: Add ToTokens for Option<T>
syntax: Add ToTokens for Attribute_
syntax: Generalize ToTokens impl for Vec<T>

It will now `flat_map` over the elements of a `Vec<T>` if
`T: ToTokens`
Disallow importing from types when reexport is involved
syntax: Add quote_method!
lint: add method to get level of a specific lint.

This allows lint traversals to emit more information (when a lint is
non-allow), or avoid doing expensive computations (when a lint is
allow).
syntax: Add ToTokens impl for Method
Small fixes for tutorial.

5.2 Simplify example to remove hidden #[deriving(Show)].
    Add example for constructing the enums.

8   Reference later sections describing rc, gc and send.
    Fix for #15293.

13  Simplify BananaMania example to remove hidden code.

17  Gave an example using the derived Rand trait.

Removed references to removed 'extra' crate.
Rename functions in the CloneableVector trait

* Deprecated `to_owned` in favor of `to_vec`
* Deprecated `into_owned` in favor of `into_vec`

[breaking-change]
str: Add better tests for string slice's Chars iterator

Test using for ch s.chars() { black_box(ch) } to have a test that should
force the iterator to run its full decoding computations.
core::str: Implement Chars iterator using slice::Items

Re-use the vector iterator to implement the chars iterator.

The iterator uses our guarantee that the string contains valid UTF-8,
but its only unsafe code is transmuting the decoded u32 into char.
Add more tests for str Chars iterator

Test iterating (decoding) every codepoint.
auto merge of #15719 : michaelwoerister/rust/global_var_null_span_fix, r=alexcrichton

This should fix issue #15541. It would be good to have an test case for this would also be nice but I haven't had the time to write one. The change is very small though and it doesn't break anything in the existing test suite, so I guess we can add it without test for now.
Guide: strings
sync: Ensure try_send() wakes up receivers

This branch of try_send() just forgot to wake up any receiver waiting for data.

Closes #15761
auto merge of #15593 : steveklabnik/rust/string_guide, r=kballard

I decided to change it up a little today and hack out the beginning of the String guide. Strings are different enough in Rust that I think they deserve a specific guide, especially for those who are used to managed languages.

I decided to start with Strings because they get asked about a lot in IRC, and also based on discussions like this one on reddit: http://www.reddit.com/r/rust/comments/2ac390/generic_string_literals/

I blatantly stole bits from our other documentation on Strings. It's a little sparse at current, but I wanted to start somewhere.

I am not exactly sure what should go in "Best Practices," and would like the feedback from the team on this. Specifically due to comments like this one: http://www.reddit.com/r/rust/comments/2ac390/generic_string_literals/citmxb5