Special packing for complex, specialize packing for avx2 #132

Job	Run time
miri	4m 49s
nostd-build (1.41.1, false, thumbv6m-none-eabi)	1m 15s
nostd-build (stable, false, thumbv6m-none-eabi)	1m 18s
tests (1.41.1, false, ubuntu-latest, x86_64-unknown-linux-gnu, cgemm)	1m 54s
tests (stable, false, ubuntu-latest, x86_64-unknown-linux-gnu, threading cgemm, yes_examples, yes...	2m 52s
tests (nightly, false, ubuntu-latest, x86_64-unknown-linux-gnu, avx)	28s
tests (nightly, ubuntu-latest, x86_64-unknown-linux-gnu, threading cgemm, fma, false)	56s
tests (nightly, ubuntu-latest, i686-unknown-linux-gnu, cgemm, sudo apt-get update sudo apt-get in...	1m 18s
tests (stable, false, macos-latest, x86_64-apple-darwin, threading cgemm, yes_examples)	2m 7s
cross_test (stable, aarch64-unknown-linux-gnu, constconf cgemm threading)	2m 5s
cross_test (1.61.0, aarch64-unknown-linux-gnu, cgemm)	2m 14s
cross_test (1.41.1, aarch64-unknown-linux-gnu, cgemm)	6m 25s
	27m 41s

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