General two-norm estimator
This PR adds:
- A general two-norm estimator based on iterative algorithm (xgenm2). A testing using xlatms to generate the matrix is provided.
- the xgemv kernels and associated tasks
- kernels to convert a real array to a complex one.
- xlange is extended to support ChamTwoNorm with a tolerance of 1.e-1
Edited by Mathieu Faverge