Port of stb_image optimized paeth unfiltering #627

Job	Run time
powerpc_cross	18s
rustfmt	12s
feature_check	1m 6s
build (1.57.0, ubuntu-latest)	1m 2s
feature_check (benchmarks)	1m 1s
test_all	3m 21s
build (1.57.0, windows-latest)	1m 13s
build (1.57.0, macos-latest)	54s
build (stable, ubuntu-latest)	15s
build (stable, windows-latest)	40s
build (stable, macos-latest)	23s
build (beta, ubuntu-latest)	17s
build (beta, windows-latest)	27s
build (beta, macos-latest)	16s
build (nightly, ubuntu-latest)	14s
build (nightly, windows-latest)	26s
build (nightly, macos-latest)	19s
	12m 24s

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