rust.md: Explicitly point out how special `'static` is.

Drive-by: fix description of `&content` to point out that `&'f type`
is (as of today) only for type expressions.
Sort most attributes alphabetically
librustc: Use separate stack slot for each return.
Reenable ignored test and add run-pass test.
librustc: Add an intrinsic to retrieve the return pointer of a function.

This is needed for some GC stuff in Servo.
librustc: Don't allow return_address intrinsic in functions that don't use an out pointer.
librustc: Don't use Load/Store for structural values.
librustc: Don't use an alloca per return if the function doesn't have nested returns.
guide-runtime.md: remove redundant verb
guide-testing.md: add auxiliary verb
guide-unsafe.md: fix noun
Minor changes to `rust.md`, and `guide-ffi.md`.

  * `rust.md`: whanges for consistency

  * `guide-ffi.md`: wrapped inline code
~ -> Box in the manual

Fixes #16439
libsyntax: Don't strip types and lifetimes from single-segment paths in
patterns.

This breaks code like:

    fn main() {
        match Some("foo") {
            None::<int> => {}
            Some(_) => {}
        }
    }

Change this code to not contain a type error. For example:

    fn main() {
        match Some("foo") {
            None::<&str> => {}
            Some(_) => {}
        }
    }

Closes #16353.

[breaking-change]
auto merge of #16081 : luqmana/rust/nr, r=pcwalton

Fixes #15763
guide-unsafe.md: fix wording

Following a suggestion by Huon Wilson.
auto merge of #16454 : pcwalton/rust/types-in-path-patterns, r=brson

patterns.

This breaks code like:

    fn main() {
        match Some("foo") {
            None::<int> => {}
            Some(_) => {}
        }
    }

Change this code to not contain a type error. For example:

    fn main() {
        match Some("foo") {
            None::<&str> => {}
            Some(_) => {}
        }
    }

Closes #16353.

[breaking-change]

r? @huonw
Enable deprecation lint on crate-local items

Previously the lint considered cross-crate items only. That's
appropriate for unstable and experimental levels, but not for
deprecation.

Closes #16409

Due to deny(deprecation), this is a:

[breaking-change]
Deprecation fallout in libcollections
Deprecation fallout in libsync