Prevent a divide-by-zero bug in SHAPE_ARC::ConvertToPolyline.
When the radius is zero, just use the initial angle (it makes
no different anyway, the result is the centre point, which is
the start point.
Corrects an error in polyline estimation
Syncs graphics to world PNS by whole layer set rather than
individual layer at a time.
Prevents reloading of full pns TOOL_BASE during reset of tools unless
the tool is being activated.
Fixes: lp:1766626
* https://bugs.launchpad.net/kicad/+bug/1766626
John Beard
Tomasz Włostowski
Seth Hillbrand
Maciej Suminski