rustdoc: inherited vis. for struct variant fields

Teach rustdoc that struct variant fields have inherited visibility.

Fix #19048
Documentation fix for std::num::strconv

- int_to_str_bytes_common() doesn't have a return value.
- float_to_str_bytes_common() has an old-style doc comment.
Fixed iOS build after Iter stab
Fix example code for unreachable!

The previous code was giving an incorrect result (not x/3).
debuginfo: Make variables captured in unboxed closures available in debuginfo.
auto merge of #19349 : tomjakubowski/rust/rustdoc-struct-variant-vis, r=sfackler

Teach rustdoc that struct variant fields have inherited visibility.

Fix #19048
auto merge of #19354 : barosl/rust/strconv-doc-fix, r=steveklabnik

- `int_to_str_bytes_common()` doesn't have a return value.
- `float_to_str_bytes_common()` has an old-style doc comment.
librustrt: stack_overflow support mipsel linux
auto merge of #19355 : vhbit/rust/ios-backtrace-fix, r=alexcrichton
auto merge of #19360 : olivren/rust/master, r=Gankro

The previous code was giving an incorrect result (not x/3).

Also, this function does not work with signed integers. It now accepts `u32` instead of `i32`.
auto merge of #19363 : michaelwoerister/rust/support-unboxed-closures, r=alexcrichton

This PR lets `rustc` generate debuginfo for variables captured by unboxed closures. 

Fixes #19356

@nikomatsakis This PR will probably conflict with #19338. If this gets merged before, you should be able to just leave the test case as it is (maybe remove the `#![feature(unboxed_closures)]` directive).
auto merge of #19366 : liigo/rust/mipsel-linux, r=alexcrichton

Since #19076 was merged, I believe mipsel + linux maybe need add to the list here, too.
reword faq to remove reference to indexing strings

Fixes #19344
auto merge of #19345 : steveklabnik/rust/gh19344, r=alexcrichton

Fixes #19344
save-analysis: emit names of items that a glob import actually imports.

There is also some work here to make resolve a bit more stable - it no longer overwrites a specific import with a glob import.

[breaking-change]

Name resolution previously had a bug where you could import an item multiple times using globs without the unused import lint noticing. That is fixed, so if you have the unused import lint on, then you may get alerted to unused imports.
Add some impls of Show (RefCell, Weak, some resolve types)
Fix fallout