Investigate premature xtol termination in trust_solve.m

Commit aa8439d4 introduced the additional termination criterion

   % Tests for termination and stringent tolerances.
    if max(.1*delta, pnorm)<=10*eps(xnorm)*xnorm
        % xtol is too small. no further improvement in
        % the approximate solution x is possible.
        info = 5;
        x(:) = inf;
        errorflag = true;
        continue
    end

This causes steady-state finding to fail in master where it worked in 5.x. An example is the attache file.

Bench.zip