Curves - Snapping to vertices while using freehand Draw tool

Adapt the snapping behavior so it snaps while we are still drawing a curve with the Draw tool.

Currently, when Snapping is active, and set to Vertex for example, we can"t draw and snap at the same time. The snapping should be available either at start (first mouse click to create the spline) or when finishing the drawing of the spline (mouse click release validates if the snapping occurs).