GELQS, GEQRS outdated

[angsch]

Please consider deprecating GELQS and GEQRS.

• There is no easy way to query the workspace to actually use the routines
• The documentation has errors (especially GELQS)
• The triangular system could do with a check of the diagonal for zeros, i.e., be solved with TRTRS, and not TRSM

GELS is a better and safer alternative. GELS wraps the matrix factorization (which GE[LQ,QR] require as input), the right-hand side transform and the solution of the triangular system in a coherent form. It solves a strict superset of what GE[LQ,QR]S can solve.

If you prefer to fix the routines rather than deprecating them, I am happy to create a PR.

[langou]

Oh my. This is ugly. This happened on or before LAPACK 3.0. So back in 1999.

I think the reason for GELQS to still exist in TESTING/LIN is because people still wanted to test DGELQF and DORMLQ and did not want to rewrite the tester. Ditto for QR.

I am not sure what to do.

Option 1: we remove/deprecate GELQS and GEQRS and rewrite the tester using GELS.

Option 2: we rename GELQS and GEQRS and give them cryptic testing names. DGETQRS01 for example.

Option 3: we just leave at that. Note that GELQS and GEQRS are not in liblapack.a. So we decide that this is not too much an issue.

In any case, thanks for point this out.

@angsch: @weslleyspereira and I are comfortable with any solution you deem appropriate and are happy with a PR.

[angsch]

I can give Option 1 a try; may take a bit of time though.