Allow to make k equal to n

By setting to -1. This is useful e.g. for gemm.

added 5 commits

• 02c29143...8ba14f21 - 4 commits from branch solverstack:master
• 12cf02e9 - Allow to make k equal to n

Compare with previous version

enabled an automatic merge when the pipeline for 12cf02e9 succeeds

merged

mentioned in commit 72f70112