Consider adding graceful death flag for linear solvers

[pelesh]

In a few unlikely situations, a linear solver may encounter an irrecoverable error (e.g. a symbolic factorization fails). It would be good to have a mechanism in HiOp to exit gracefully with appropriate error message in those situations. For example, if matrixChanged() function returns -1, HiOp will try to regularize matrix. Perhaps consider introducing error codes for linear solver interface functions that would mark an irrecoverable error?

Having mechanism like this would help debug code, because the execution will terminate right after encountering the error and appropriate error message would be provided.

@cnpetra @kswirydo