Fix segfault when complex double matrix calls ZGETRF (bug #45577). * CMatrix.cc (finverse, determinant, rcond, fsolve): Calculate norm of matrix and if it is NaN, skip calling ZGETRF in LAPACK and set info to non-zero value to signal an error.

# persistent_nest
function y = persistent_nest ()
  persistent x = 0;
  g;
  y = x;

  function g
    x = x + 1;
  end
end