properly handle first segment of waypoints

[nczempin]

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When fixing issue #23, I factored out the path drawing code in the hope that I could just call it an additional part for the first segment (from the ship to the first waypoint). However, it looks like this first segment animates too quickly; most likely this is related to the length calculation.

@PriorBlue, you'll probably figure out the cause of this much quicker than I would.

[nczempin]

With the new AI system, the first segment doesn't animate more quickly any more, but the path starts at the way point now, which is behind the creep most of the time.

I would consider this a regression on what we had previously. @PriorBlue, were you planning to return to starting the path at the ship location rather than at the way point?