Text positioning when printing - vertical graphics context resolution (#356)

- vertical graphics context resolution has been used incosistently which leads to wrongly positioned texts when printing

Source/Text/GdiFontDefn.cs

@@ -37,7 +37,7 @@ namespace Svg
             var ff = _font.FontFamily;
             float ascent = ff.GetCellAscent(_font.Style);
             float baselineOffset = _font.SizeInPoints / ff.GetEmHeight(_font.Style) * ascent;
-            return renderer.DpiY / 72f * baselineOffset;
+            return SvgDocument.PointsPerInch / 72f * baselineOffset;
         }
 
         public IList<RectangleF> MeasureCharacters(ISvgRenderer renderer, string text)

Source/Text/SvgFontDefn.cs

@@ -39,7 +39,7 @@ namespace Svg
         {
             float ascent = _font.Descendants().OfType<SvgFontFace>().First().Ascent;
             float baselineOffset = this.SizeInPoints * (_emScale / _size) * ascent;
-            return renderer.DpiY / 72f * baselineOffset;
+            return SvgDocument.PointsPerInch / 72f * baselineOffset;
         }
 
         public IList<System.Drawing.RectangleF> MeasureCharacters(ISvgRenderer renderer, string text)