Just a quickie feature I needed here at work- the previous linear interpolation of tilt in curves can give nasty pinching problems when trying to do flowing curves like a ribbon. This commit lets you choose the interpolation type, between Linear, Cardinal, and BSpline. The code was already set up for it pretty easily, mainly needed to make the choice visible to the user. Example: http://mke3.net/blender/devel/etc/tilt_interp_types.png Works on selected curve 'lines', menu in 'curve tools' panel in edit mode.