linef(lambda, fn, x, d) calculates the value of the function
fn at the point x+lambda*d. Here x is a row vector
and lambda is a scalar.
linef(lambda, fn, x, d, p1, p2, ...) allows additional
arguments to be passed to fn().
This function is used for convenience in some of the optimisation routines.
linemin.
gradchek, lineminCopyright (c) Ian T Nabney (1996-9)