Add C++ implementations for xLAPY2 and xLAPY3. They are straight translations of the corresponding Fortran code, even though xLAPY2 can just call std:hypot.

The code currently lives in eigen3/lapack/experimental. The plan is to finish development here, and once its done upstream it replacing all the f2c'ed code.

PiperOrigin-RevId: 380897335
3 files changed