`__heap_base` and `__data_end` are exported for use by wasm-bindgen, which
uses the wasm32-unknown-unknown target. On wasm32-wasi, as a step toward
implementing the Canonical ABI, and as an aid to building speicalized WASI
API polyfill wrappers, don't export `__heap_base` and `__data_end` on
wasm32-wasi.

Since rust-lang#72889, the Rust wasm target doesn't use --passive-segments, so
remove the `--export=__wasm_init_memory`.

As documented in the [tool-conventions Linking convention],
`__wasm_init_memory` is not intended to be exported.

[tool-conventions Linking convention]: https://github.com/WebAssembly/tool-conventions/blob/7c064f304858f67ebf22964a84b7e9658e29557a/Linking.md#shared-memory-and-passive-segments

Fixes a regression caused by 8846c08, where
a header's top margin used to be collapsed, but isn't any more.

…tmcm

Add negation methods for signed non-zero integers.

Performing negation with defined wrapping semantics (such as `wrapping_neg()`) on a non-zero integer currently requires unpacking to a primitive and re-wrapping. Since negation of non-zero signed integers always produces a non-zero result, it is safe to implement the various `*_neg()` methods for `NonZeroI{N}`.

I'm not sure what to do about the `#[unstable(..., issue = "none")]` here -- should I file a tracking issue, or is that handled by the Rust dev team?

ACP: rust-lang/libs-team#105

…port-heap-base, r=davidtwco

Don't export `__heap_base` and `__data_end` on wasm32-wasi.

`__heap_base` and `__data_end` are exported for use by wasm-bindgen, which uses the wasm32-unknown-unknown target. On wasm32-wasi, as a step toward implementing the Canonical ABI, and as an aid to building speicalized WASI API polyfill wrappers, don't export `__heap_base` and `__data_end` on wasm32-wasi.

…it-memory, r=nagisa

Don't export `__wasm_init_memory` on WebAssembly.

Since rust-lang#72889, the Rust wasm target doesn't use --passive-segments, so remove the `--export=__wasm_init_memory`.

As documented in the [tool-conventions Linking convention], `__wasm_init_memory` is not intended to be exported.

[tool-conventions Linking convention]: https://github.com/WebAssembly/tool-conventions/blob/7c064f304858f67ebf22964a84b7e9658e29557a/Linking.md#shared-memory-and-passive-segments

… r=jsha

rustdoc: cut margin-top from first header in docblock

Fixes a regression caused by 8846c08, where a header's top margin used to be collapsed, but isn't any more.

## Before

![image](https://user-images.githubusercontent.com/1593513/192893092-8e158bf7-ae18-41ef-8f11-6f34c724d345.png)

## After

![image](https://user-images.githubusercontent.com/1593513/192893139-d6ee06bf-9c0b-4194-bd5d-636312c89367.png)