pdf: add splines

This is identical to the code in draws in ps.

pdf.c

@@ -962,11 +962,21 @@ void drawa(int h1, int v1, int h2, int v2)
 	drawl(h1 + h2, v1 + v2);
 }
 
-/* draw an spline */
+/* draw a spline */
 void draws(int h1, int v1, int h2, int v2)
 {
+	int x0 = o_h;
+	int y0 = o_v;
+	int x1 = x0 + h1;
+	int y1 = y0 + v1;
+	int x2 = x1 + h2;
+	int y2 = y1 + v2;
+
+	sbuf_printf(pg, "%s ", pdfpos((x0 + 5 * x1) / 6, (y0 + 5 * y1) / 6));
+	sbuf_printf(pg, "%s ", pdfpos((x2 + 5 * x1) / 6, (y2 + 5 * y1) / 6));
+	sbuf_printf(pg, "%s c\n", pdfpos((x1 + x2) / 2, (y1 + y2) / 2));
+
 	outrel(h1, v1);
-	sbuf_printf(pg, "%s l\n", pdfpos(o_h, o_v));
 }
 
 void docheader(char *title, int pagewidth, int pageheight, int linewidth)