improve controls

Signed-off-by: Pekka Enberg <penberg@iki.fi>
Fix position coordinate truncation

The position coordinate must not be converted to int; otherwise player
movement will be jumpy.  The reason we do it for map coordinates is
because we want the intersection rays to end at map block edges.

Signed-off-by: Pekka Enberg <penberg@iki.fi>
Make movement smoother

Signed-off-by: Pekka Enberg <penberg@iki.fi>