Refactor nut to allow hex nut

[Amadeus]

Currently you can modify

threadlib/threadlib.scad

Line 60 in d8c8384

 cylinder(h=H, d=Douter, $fn=fn); 

to set $fn=6 to obtain a hex nut:

However, you don't want to pass fn=6 into the nut module otherwise the resolution of the thread will be affected.

Can we refactor the nut module to allow for hex nuts?

[Adrian Schlatter]

How would you want to refactor nut(...)?