Add P3050R1 ("Fix C++26 by optimizing linalg::conjugated for noncomplex value types")

[mhoemmen]

Abstract:

We propose the following change to the C++ Working Paper. If an mdspan object x has noncomplex value_type, and if that mdspan does not already have accessor type conjugated_accessor<A> for some nested accessor type A, then we propose to change conjugated(x) just to return x. Delaying this until after C++26 would be a breaking change.

I submitted this today (2024/04/08) as P3050R1.

This supersedes PR https://github.com/ORNL/cpp-proposals-pub/pull/437 , which I created in November 2023, and which still hasn't been merged.