Better numerical robustness for stroking #389

Job	Run time
cargo test msrv	3m 41s
cargo test nightly (macOS-latest)	1m 15s
cargo fmt	20s
cargo test nightly (windows-2019)	1m 24s
Docs (macOS-latest)	57s
cargo test nightly (ubuntu-latest)	43s
cargo clippy+test (macOS-latest)	1m 35s
Docs (windows-2019)	1m 19s
cargo clippy+test (windows-2019)	3m 39s
Docs (ubuntu-latest)	31s
cargo clippy+test (ubuntu-latest)	1m 27s
cargo clippy+test (wasm32) (macOS-latest)	1m 7s
cargo clippy+test (wasm32) (windows-2019)	2m 6s
cargo clippy+test (wasm32) (ubuntu-latest)	49s
	20m 53s

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