Fix old-style format string to prepare for future Clippy.

spsc: fix future clippy warning

Upgrade day-to-day toolchain to current stable.

Update pin-project to stop Clippy warnings in output.

Update deps in lockfile (should not affect users)

Version 1.3.0.

RELEASE-NOTES: document internal changes since 1.2

Disable building against the Beta toolchain.

Reword doc comments to pacify nightly Clippy.

RELEASE-NOTES: note PeriodicGate::is_lagging.

time: add way to query if a gate is lagging.

Indent some comments as clippy has gotten picky.

Switch to portable-atomic.

mutex: fix create_static_mutex docs

os: fix an example in a comment