[beta] Backport accepted PRs to 1.21

[dtolnay]

Backport of:

• don't suggest placing use statements into expanded code #44215
• stabilize tcpstream_connect_timeout #44563
• stabilized iterator_for_each #44567
• travis: Move sccache to the us-west-1 region #44574
• stabilized ord_max_min #44593
• stabilized compiler_fences #44595
• ci: Upload/download from a new S3 bucket #44617
• stabilized needs_drop #44639
• Stabilized vec_splice and modified splice tracking issue #44640
• Backport libs stabilizations to 1.21 beta #44824

[kennytm]

Please update https://github.com/dtolnay/rust/blob/5f502de51dd01b3bf06f874b87702445a0ae8d90/src/liballoc/string.rs#L2253 as well.

[00:04:19] tidy error: /checkout/src/liballoc/string.rs:2253: mismatches to previous in: ["tracking issue"]

[alexcrichton]

r=me wit hthe tidy error fixed,

thanks @dtolnay!

[alexcrichton]

r=me wit hthe tidy error fixed,

thanks @dtolnay!

[dtolnay]

@bors r=alexcrichton

[bors]

📌 Commit a03e765 has been approved by alexcrichton

[alexcrichton]

@bors: r-

backport fails to compile?

[dtolnay]

I removed the backport of #44215 from this PR, will leave that one to someone else.

(expand) Here is the merge I botched.

            match item.node {
                ItemKind::Use(..) => {
                    // don't suggest placing a use before the prelude
                    // import or other generated ones
<<<<<<< HEAD
                    if item.span == DUMMY_SP {
                        let mut span = item.span;
                        span.hi = span.lo;
                        self.span = Some(span);
||||||| parent of 74748b11bb3... WIP: don't suggest placing `use` statements into expanded code
                    if item.span == DUMMY_SP {
                        self.span = Some(item.span.with_hi(item.span.lo()));
=======
                    if item.span.ctxt().outer().expn_info().is_none() {
                        self.span = Some(item.span.with_hi(item.span.lo()));
>>>>>>> 74748b11bb3... WIP: don't suggest placing `use` statements into expanded code
                        self.found_use = true;
                        return;
                    }
                },
                // don't place use before extern crate
                ItemKind::ExternCrate(_) => {}
                // but place them before the first other item
                _ => if self.span.map_or(true, |span| item.span < span ) {
<<<<<<< HEAD
                    let mut span = item.span;
                    span.hi = span.lo;
                    self.span = Some(span);
||||||| parent of 74748b11bb3... WIP: don't suggest placing `use` statements into expanded code
                    self.span = Some(item.span.with_hi(item.span.lo()));
=======
                    if item.span.ctxt().outer().expn_info().is_none() {
                        // don't insert between attributes and an item
                        if item.attrs.is_empty() {
                            self.span = Some(item.span.with_hi(item.span.lo()));
                        } else {
                            // find the first attribute on the item
                            for attr in &item.attrs {
                                if self.span.map_or(true, |span| attr.span < span) {
                                    self.span = Some(attr.span.with_hi(attr.span.lo()));
                                }
                            }
                        }
                    }
>>>>>>> 74748b11bb3... WIP: don't suggest placing `use` statements into expanded code
                },

[alexcrichton]

@bors: r+

[bors]

📌 Commit f38d353 has been approved by alexcrichton

[alexcrichton]

@bors: p=1 (backport)

[bors]

⌛️ Testing commit f38d353 with merge 3c3cd3f...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: alexcrichton
Pushing 3c3cd3f to beta...