The introduced dependency on `getauxval`causes linking
problems with musl, see rust-lang#89626.

 - Remove border.
 - Reduce size of emoji slightly.
 - Remove details disclosure for unstable reason. This was inconsistent
   with our other details disclosures, and the detail revealed was
   usually better explained by clicking on the issue link.

Methods that were only blocked on `const_panic` have been stabilized.
The remaining methods of `duration_consts_2` are all related to floats,
and as such have been placed behind the `duration_consts_float` feature
gate.

This is a step toward adding more test coverage to make it easier to
remove the distinction between collapsed and uncollapsed doc values.

…s, r=oli-obk

Partially stabilize `duration_consts_2`

Methods that were only blocked on `const_panic` have been stabilized.
The remaining methods of `duration_consts_2` are all related to floats,
and as such have been placed behind the `duration_consts_float` feature
gate.

…mics_for_musl, r=workingjubilee

Restrict aarch64 outline atomics to glibc for now.

The introduced dependency on `getauxval` causes linking problems with musl, making compiling any binaries for `aarch64-unknown-linux-musl` impossible without workarounds such as using lld or adding liblibc.rlib again to the linker invocation, see rust-lang#89626.

This is a workaround until libc>0.2.108 is merged.

…ature, r=camelid

Create rustdoc_internals feature gate

As suggested by `@camelid` [here](rust-lang#90398 (comment)), since `doc_keyword` and `doc_primitive` aren't meant to be stabilized, we could put them behind a same feature flag.

This is pretty much what it would look like (needs to update the tests too).

The tracking issue is rust-lang#90418.

What do you think `@rust-lang/rustdoc` ?

Reduce prominence of item-infos

Fixes rust-lang#59853

 - Remove border.
 - Reduce size of emoji slightly.
 - Remove details disclosure for unstable reason. This was inconsistent with our other details disclosures, and the detail revealed was usually better explained by clicking on the issue link.

Demo: https://rustdoc.crud.net/jsha/chill-item-info/std/mem/union.MaybeUninit.html#method.slice_assume_init_ref

Compare vs: https://doc.rust-lang.org/nightly/std/mem/union.MaybeUninit.html#method.slice_assume_init_ref

<img src="https://user-images.githubusercontent.com/220205/142717815-09828c9e-6ff4-445a-8ccc-31e028fd4985.png" width=700>

Fix test in std::process on android

closes rust-lang#10380

Fix more <a> color

Fixes rust-lang#91175.

Another bug I saw is:

![Screenshot from 2021-11-24 11-41-27](https://user-images.githubusercontent.com/3050060/143239845-f173cfeb-8f5c-4215-a5af-b71d4e1bcd84.png)

I fixed it as well.

r? `@jsha`

…meGomez

rustdoc: Add test for mixing doc comments and attrs

This is a step toward adding more test coverage to make it easier to
remove the distinction between collapsed and uncollapsed doc values.