fixing messed up test by switching to XY axis convergence in swaptionpseudojacobian.cpp. Otherwise the marketmodel tests are passing just out of luck! (as i suspect are a lot of other tests). The issue is that x-axis accuracy should only guarantee that the root is accurate to some degree, but we should be happy with being on either extreme side of the admissible interval. It is therefore possible, with say f increasing, and with using x accuracy, that the result of solving f = 0 ends up being larger than the result of solving f-e = 0, even when e > 0. If we switch to y accuracy and that we take an accuracy, say < e/2 then we are good because this guarantees correct ordering of the roots of f = 0 and f-e = 0