Corrected linearGradient members (not 0 based)

See documentation: "Linear gradients in Highcharts have a similar syntax to that of SVG" ... "linearGradient holds another object literal that defines the start position (x1, y1) and the end position (x2, y2)"
http://www.highcharts.com/docs/chart-design-and-style/colors
http://www.w3schools.com/svg/svg_grad_linear.asp

highcharts/highcharts.d.ts

@@ -166,7 +166,7 @@ interface HighchartsChartEvents {
 
 interface HighchartsGradient {
     linearGradient?: {
-        x0: number; y0: number; x1: number; y1: number;
+        x1: number; y1: number; x2: number; y2: number;
     };
     radialGradient?: {
         cx: number; cy: number; r: number;