Allow FillToEdge to grow when all its edges are blocked.

Allow FillToEdge to grow when all its edges are blocked.

This change points out how useless the return value from client_find_resize_directional()
was, so it also removes that.

When all edges are blocked, the FillToEdge action will try to grow all four edges agin
without blocking any of them on their current edge. This more closely matches the
behaviour of the GrowToEdge action.