implemented multiclass for svc (#308) #604

Job	Run time
check_features (ubuntu, --features serde)	32s
check_features (ubuntu, --features datasets)	22s
tests (windows, x86_64-pc-windows-msvc)	3m 9s
tests (ubuntu, i686-unknown-linux-gnu)	31s
tests (ubuntu, x86_64-unknown-linux-gnu)	1m 22s
check_features (ubuntu)	17s
tests (macos, aarch64-apple-darwin)	1m 15s
tests (ubuntu, wasm32-unknown-unknown)	1m 45s
tests (windows, i686-pc-windows-msvc)	1m 49s
	11m 2s

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