`git merge --strategy ours` to take the 0.3.5 changes for 31001,
and ignore the conflicting 0.2.9 changes.

This build was added in 0.3.5.

We need to mitigate slow scheduling of Travis macOS jobs.

Closes ticket 32177.

Stem from maint-0.3.5, disabled macOS chutney from ticket32177_029.

We need to mitigate slow scheduling of Travis macOS jobs.

Closes ticket 32177.

Instead of Windows Server 2016.

Closes ticket 32086.

Since Rust on macOS is slow, don't wait for the macOS Rust job to finish.
Instead, split rust into slow rust (macOS) and fast rust (Linux). And
allow the build to finish before slow rust finishes.

Also make sure that we have:
* a Rust build on each platform,
* a Rust build with each compiler, and
* a check on all our Rust builds.

Finally, sort builds: allow fail last, macOS first, slowest first.

Closes 31859 for 0.3.5.

Part of 31859 for 0.3.5.

While merging:
* leave out some redundant jobs and build matrix entries

Since Travis macOS has IPv6 support (and Travis Linux does not), chutney
will now run its IPv6 networks as part of Travis CI.

But since chutney is slow, don't wait for the macOS chutney to finish.
(Travis have fixed the duplicate notification bug in fast_finish. So we
can use fast_finish and allow_failure to finish early. Unfortunately,
allow_failure also means we ignore failures in macOS chutney.)

Also make sure that we have:
* a compile on each platform, with each compiler,
* a check on each platform, and
* a check on each compiler.

Finally, sort builds: allow fail last, macOS first, slowest first.

Closes ticket 30860.
Closes ticket 31859 for 0.2.9.

Part of 31859.

When Appveyor fails before the install step, some of the finish step's
functions were not defined.

Fixes bug 31884; bugfix on 0.3.4.2-alpha.

The jobs should be the same, but Travis may display them differently.

Part of 31859.

Frequently, when a patch fails, it has failures in several files.
Using the "-k" flag will let us learn all the compilation errors,
not just the first one that the compiler hits.

Based on a patch by rl1987.

Closes ticket 31372.

Frequently, when a patch fails, it has failures in several files.
Using the "-k" flag will let us learn all the compilation errors,
not just the first one that the compiler hits.

Based on a patch by rl1987.

"ours" merge to avoid picking up 0.2.9 version of ticket 31673.

Our code assumes that when we're configured to get IPv6 addresses
out of a TRANS_PF transparent proxy connection, we actually will.
But we didn't check that, and so FreeBSD started warning us about a
potential NULL pointer dereference.

Fixes part of bug 31687; bugfix on 0.2.3.4-alpha when this code was
added.

We used to do this on Windows only, but it appears to affect
multiple platforms when building with certain versions of GCC, and a
common pattern for defining the floating-point classifier functions.

Fixes part of 31687. I'm calling this a bugfux on 31687, when we
started suppressing these warnings on Windows.

Closes #31673

Closes #31673

When tor is missing descriptors for some primary entry guards, make the
log message less alarming. It's normal for descriptors to expire, as long
as tor fetches new ones soon after.

Fixes bug 31657; bugfix on 0.3.3.1-alpha.