Fix linear vectorized transversal in linspace (fixes bug 526).
(transplanted from 8a36e91732b73527c6fdf42d79952290d3e753da)

--HG--
branch : 3.1
extra : transplant_source : %8A6%E9%172%B75%27%C6%FD%F4-y%95%22%90%D3%E7S%DA