hpipm‘s API was modified

[gannerfreer]

The API of HPIPM has undergone changes, which may lead to errors in C++ implementations.

Specifically, the parameters for the function d_ocp_qp_set_all were modified three weeks ago.

[alexliniger]

The most straightforward fix is to check out the hash before the change, f7951846e9240fa05cdb3116b8cd5d60acaff09a this should be safe I think.

Generally I should have fixed all my third party dependency to working hashes.

[Lucien950]

+1