Implement the support for the `_Fcomplex` and `_Dcomplex` types used by MSVC in place of the standard C99 complex types. This is necessary to make LAPACK build out of the box with MSVC, since it does not implement the default C99 types. See: https://learn.microsoft.com/en-us/cpp/c-runtime-library/complex-math-support I went for the simplest implementation possible, limiting the changes to swapping the default types used when MSVC is used as the compiler, also when `lapack_config.h` is not used. I haven't added a `LAPACK_COMPLEX_*` ifdef for it, but I can do that if you prefer. Signed-off-by: Michał Górny <mgorny@quansight.com>