connect loose ends to the rest of the print.

[rewolff]

Is your feature request related to a problem? Please describe.
In wing-type shapes, there is always a "sharp" end.

In the attached slice, the part that was too thin to be printed with two permimeters is printed with onie, but the way slic3r detaches it from the rest means that it won't stick to the rest and will fall off.

Describe the solution you'd like
In these cases, it would be advantageous to make the outer perimeter start at the "loose end". So the part that is now separate and will be completely loose in the final print would be the start and end of the outer perimeter. Either start at the trailing edge of the wing and go around the whole wing and end where things get too thin to print with two or the other way around.