Altium PCB: convert small arcs in line chain to segments to avoid overflow issues.

Can be seen on "mb1932-bdp", for example.

(cherry picked from commit e6ce4eb73e)

pcbnew/pcb_io/altium/altium_pcb.cpp

@@ -109,14 +109,33 @@ void HelperShapeLineChainFromAltiumVertices( SHAPE_LINE_CHAIN& aLine,
             VECTOR2I arcStart = vertex.center + arcStartOffset;
             VECTOR2I arcEnd   = vertex.center + arcEndOffset;
 
+            bool isShort = arcStart.Distance( arcEnd ) < pcbIUScale.mmToIU( 0.001 )
+                           || angle.AsDegrees() < 0.2;
+
             if( arcStart.Distance( vertex.position )
                     < arcEnd.Distance( vertex.position ) )
             {
-                aLine.Append( SHAPE_ARC( vertex.center, arcStart, -angle ) );
+                if( !isShort )
+                {
+                    aLine.Append( SHAPE_ARC( vertex.center, arcStart, -angle ) );
+                }
+                else
+                {
+                    aLine.Append( arcStart );
+                    aLine.Append( arcEnd );
+                }
             }
             else
             {
-                aLine.Append( SHAPE_ARC( vertex.center, arcEnd, angle ) );
+                if( !isShort )
+                {
+                    aLine.Append( SHAPE_ARC( vertex.center, arcEnd, angle ) );
+                }
+                else
+                {
+                    aLine.Append( arcEnd );
+                    aLine.Append( arcStart );
+                }
             }
         }
         else