hkd32

bip32: Fix no-std support with `secp256k1-ffi` feature flag (#1254) #817

Job	Run time
build (1.60.0, armv7a-none-eabi)	1m 9s
build (1.60.0, thumbv7em-none-eabi)	1m 10s
test (ubuntu-latest, 1.60.0)	1m 10s
test (ubuntu-latest, stable)	16s
build (1.60.0, wasm32-unknown-unknown)	1m 7s
test (macos-latest, 1.60.0)	1m 8s
build (stable, armv7a-none-eabi)	18s
test (macos-latest, stable)	14s
build (stable, thumbv7em-none-eabi)	10s
build (stable, wasm32-unknown-unknown)	9s
test (windows-latest, 1.60.0)	1m 48s
test (windows-latest, stable)	48s
	9m 27s

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