Update the Machine Epsilon parameter.

Used in numerical routines.
Pre-condition the coefficients in quadratic solver

We need well conditioned quadratics to guarantee numerical accuracy.
Boolean: handle linear segments correctly.

Earlier implementation was unfinished and did not reset some handles to
linear, this caused the winding to be miscalculated.
Remove the debug code in curve#solveCubic

The cubic and quadratic solver has been tested with > 2 million
equations as of now. We need more rigorous tests however.