GT2 timing belt profile

 A couple of OpenSCAD functions to generate GT2 profile timing belts.

This generates belts by concatenating 5 (now 3, mirrored) arches, following specifications for the tooth profile that I have found online. It can also generate pulleys, and with some effort probably curved sections of belt, but I don't really have an use case for this last function

Updates:
I have fixed the “remove doubles” features, so now the pulleys are generated correctly without needing to offset the points twice. 
I have modified the function that generates the tooth profile, now it creates two half-teeth (one mirrored), which will hopefully make it possible to start a sequence of teeth selectively on a peak or a trough.
The function that generates pulleys has been extended to allow generating a pulley section of a nominal radius: if a radius is specified that is greater than that of the circle that could be made with the number of teeth chosen then only a partial arc will be rendered.
The function that generates pulleys has also been extended to allow inverting the tooth profile, essentially generating a gt2 “gear”. This could probably be used to try and print closed belts, and eventually to render a complex belt path.