This is a legacy constant and it's better to just use `i32::MAX`. Note
that one cannot `use` an associated constant so this just removed the
import. This is better anyway since it's only used once and it didn't
provide meaningful line length reduction.

Rust is now checking cfg attributes for typos but this interferes with
our cfgs that rustc/cargo don't recognize. This whitelists them so they
no longer produce warnings.

The newest nightly stabilized `PanicMessage` with a slightly different
API. This updates the API and removes the `#![feature()]` attribute.

Despite using the `#![feature()]` attribute rustc still warns about it
being unstable. Changing it to `libc::abort` gets rid of the annoying
message.

Previously we had dependency problems that were resolved by resolver v2.
We want to activate it just in case it happens again but even better,
bump the edition.  This was probably forgotten when other crates were
migrated.

The `no_std` test disables `std`, so unwinding is unsupported, so we use
`panic = "abort"` but the `core` library is compiled with unwind by
default which breaks the build. Xargo can handle this by recompiling
`core` with `panic = "abort"` so we use it.

This can help debug CI issues.

Cross uses an old image by default and there's a problem that is
resolved in the newest wine version, so this commit upgrades the
image.