For several packet types, `abs2` was not vectorized even if it only requires `pmul`. Get rid of the confusing and redundant `HasAbs2` enum and instead check `HasMul` in addition to making sure the scalar type is not complex.
See merge request libeigen/eigen!2048
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### Description
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Allow user to configure if `free` is allowed at runtime.
Reverts to Eigen 3.4 behavior by default, where `free(...)` is allowed if `EIGEN_RUNTIME_NO_MALLOC` is defined but `set_is_malloc_allowed(true)`. Adds a separate `set_is_free_allowed(...)` to explicitly control use of `std::free`.
### Reference issue
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Fixes#2983.
### Additional information
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Closes#2983
See merge request libeigen/eigen!2047
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### Description
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Support AVX for i686.
There was an existing work-around for windows. Added the more generic
architecture comparison to also apply for linux.
### Reference issue
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Fixes#2991.
Closes#2991
See merge request libeigen/eigen!2037
