Add initial line segment when adding arc to wxGraphicsPath with GDI+

For the sake of compatibility with Cairo (and Direct2D) an initial line segment should be added to the path from the current point (if set) to the beginning of the arc.

Closes #17557

interface/wx/graphics.h

@@ -31,11 +31,15 @@ public:
         The angles are measured in radians but, contrary to the usual
         mathematical convention, are always @e clockwise from the horizontal
         axis.
+
         If for clockwise arc @a endAngle is less than @a startAngle it will be
         progressively increased by 2*pi until it is greater than @a startAngle.
         If for counter-clockwise arc @a endAngle is greater than @a startAngle
         it will be progressively decreased by 2*pi until it is less than
         @a startAngle.
+
+        If there is a current point set, an initial line segment will be added
+        to the path to connect the current point to the beginning of the arc.
     */
     //@{
     virtual void AddArc(wxDouble x, wxDouble y, wxDouble r,