* Fix initialization of diagHessianBias for nn.SpatialConvolution.
* Fix computing diagHessianBias for nn.SpatialFullConvolution.
* Call module:forward() with the proper input before calling
accGradParameters(). Without that, accDiagHessianParameters()
produces incorrect results for some convolution classes.
* Move duplicate code from Module.getParameters() to Module.flatten(),
which is now used by both the original Module.getParameters() in
Module.lua and the replacement Module.getParameters() in hessian.lua.