Call rounded_square with new signature

Ah, coding without tests...
Make the clamp stronger to avoid delamination

I had partial clamp delamination under heavy clamping forces when
previously printed.  Using more material results in a much stronger
clamp.
e3d v6 version of the direct drive extruder
STL rendering of Clamp with more material
STL rendering of e3d v6 direct drive extruder