std::simd

Adds interleaved complex value support to std::simd.

Adds <bit> function overloads for std::simd.

Moves the SIMD types into namespace std::simd and renames them (vec, mask).

Fixes explicit conversions, the unsequenced attribute, identity-element position and members of disabled SIMD types.

Renames simd_split to simd_chunk.

Adds the permutation API (permute, gather/scatter forms) to std::simd.

Adds more constructors and accessors to std::simd.

Makes std::simd a range.

Settles the namespace name for SIMD (std::simd).

Adds the missing deduction guide from simd::mask to simd::vec.

Makes simd reductions SIMD-generic.

Rewords [simd.math] for consteval conversions.

Fixes integer-from conversions in [simd] (LWG4470).

Makes consteval broadcast to simd::vec value-preserving.

Adds a simd::iota object and related generators.

Adds std::simd overloads for the bit permutation functions.