…ustc source.

On my system, when the processor is already loaded, and I try to
run the test suite, e.g. compile-fail/dep-graph-assoc-type-trans.rs
fails because of undecodable JSON.

Running the compiler manually, I can see that the dep graph thread
panics (and puts non-JSON on stderr) while `send`ing on `swap_out`,
presumably because the other end has already quit.  I think that in
this case, we can just gracefully exit the thread.

Also move the "Thread type" section down a bit, since it is
not so important anymore.

Fixes: #33321

The changed line makes it look like `unsafe` is allowed, but the
first statement of `parse_item_foreign_fn` is:

`self.expect_keyword(keywords::Fn)?;`

So we get the strange "expected one of `fn`, `pub`, `static`, or
`unsafe`, found `unsafe`".

Fixes: #27361

Removed unnecessary use of threads from E0504

Cleaned up line ending on E0504

Added more examples for E0504

Changed to erroneous code wording

Switched Rc example to thread/Arc example

Added comments describing why errors no longer occur

We will no longer use `ccache` in the makefiles for our local dependencies like
miniz, but they're so small anyway it doesn't really matter.

Closes #33285

The definition of this value recently changed slightly. It no
longer corresponds directly to the target triple.

Also shuffled things around to make the order of cfg descriptions more
logical and added text related them to the target triple.

cc #33403

Doc improvement on std::fmt module

Part of #29355.

r? @steveklabnik

…komatsakis

Add `TAGS.rustc.emacs`/`TAGS.rustc.vi` make targets

Add `TAGS.rustc.emacs`/`TAGS.rustc.vi` make targets, (re-)including rustc source.

Add process types documentation

Part of #29370.

r? @steveklabnik

dep_graph: avoid panicking in thread when channel closed

On my system, when the processor is already loaded, and I try to
run the test suite, e.g. compile-fail/dep-graph-assoc-type-trans.rs
fails because of undecodable JSON.

Running the compiler manually, I can see that the dep graph thread
panics (and puts non-JSON on stderr) while `send`ing on `swap_out`,
presumably because the other end has already quit.  I think that in
this case, we can just gracefully exit the thread.

mk: Fix building with --enable-ccache

We will no longer use `ccache` in the makefiles for our local dependencies like
miniz, but they're so small anyway it doesn't really matter.

Closes #33285

std::thread docs: spawn() does not return a Thread anymore

Also move the "Thread type" section down a bit, since it is not so important anymore.

Fixes: #33321

parser: do not try to continue with `unsafe` on foreign fns

The changed line makes it look like `unsafe` is allowed, but the first statement of `parse_item_foreign_fn` is:

```
self.expect_keyword(keywords::Fn)?;
```

So we get the strange "expected one of `fn`, `pub`, `static`, or `unsafe`, found `unsafe`".

Fixes: #27361

Add detailed error explanation for E0504

Part of #32777

Replace copy-pasted variable name with relevant one

errors in the doc

Remove rust flags from doc block

Fixes #33405

r? @Manishearth

Add an example to Wrapping's documentation.

Such an example would have helped me understand `Wrapping` quicker.

r? @steveklabnik

[Doc] Default cpu is "generic" (and not "default")

See [line 305](https://github.com/phil-opp/rust/blob/a22ca2872ef6782306012e6817dc4b8b778c43e9/src/librustc_back/target/mod.rs#L305).

doc: Update reference with better description of target_env

The definition of this value recently changed slightly. It no
longer corresponds directly to the target triple.

Also shuffled things around to make the order of cfg descriptions more
logical and added text related them to the target triple.

cc #33403

Fix some some duplicate words.

Rollup of 15 pull requests

- Successful merges: #33129, #33256, #33283, #33313, #33314, #33326, #33336, #33386, #33402, #33409, #33410, #33428, #33430, #33437, #33438
- Failed merges: