g = rbfjacob(net, x)
g = rbfjacob(net, x) takes a network data structure net
and a matrix of input vectors x and returns a three-index matrix
g whose i, j, k element contains the
derivative of network output k with respect to input
parameter j for input pattern i.
rbf, rbfgrad, rbfbkpCopyright (c) Ian T Nabney (1996-9)