Port of stb_image optimized paeth unfiltering #630

Job	Run time
powerpc_cross	9s
rustfmt	14s
feature_check (ubuntu-latest)	1m 2s
build (1.57.0, ubuntu-latest)	52s
feature_check (macos-latest)	40s
build (1.57.0, windows-latest)	1m 39s
test_all (ubuntu-latest)	3m 9s
feature_check (unstable, ubuntu-latest)	59s
test_all (macos-latest)	2m 46s
feature_check (unstable, macos-latest)	37s
build (1.57.0, macos-latest)	54s
feature_check (benchmarks, ubuntu-latest)	58s
feature_check (benchmarks, macos-latest)	41s
build (stable, ubuntu-latest)	16s
build (stable, windows-latest)	46s
build (stable, macos-latest)	19s
build (beta, ubuntu-latest)	16s
build (beta, windows-latest)	40s
build (beta, macos-latest)	21s
build (nightly, ubuntu-latest)	13s
build (nightly, windows-latest)	40s
build (nightly, macos-latest)	16s
	18m 27s

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