Compatibility: Ignore textLength attribute if X attribute is list. (#374)

- ignore textLength attribute if X attribute is list
- add test images

Source/Text/SvgTextBase.cs

@@ -349,11 +349,14 @@ namespace Svg
                     if (Math.Abs(diff) > 1.5)
                     {
                         if (this.LengthAdjust == SvgTextLengthAdjust.Spacing)
+                        {
+                            if (this.X.Count < 2)
                             {
                                 origState.LetterSpacingAdjust = -1 * diff / (state.NumChars - origState.NumChars - 1);
                                 SetPath(origState, false);
                                 return;
                             }
+                        }
                         else
                         {
                             using (var matrix = new Matrix())

Tests/W3CTestSuite/svg/__pull_request-374-01.svg

+<?xml version="1.0" encoding="utf-8"?>
+<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0" y="0" width="80" height="80" xml:space="preserve">
+<text x="10,30,50"            y="15" fill="#000" font-size="14"                >ABC</text>
+<text x="10,30,50"            y="30" fill="#000" font-size="14" textLength="14">ABC</text>
+<text x="10,30,50" dx="4,4,4" y="45" fill="#000" font-size="14" textLength="14">ABC</text>
+<text x="10"                  y="60" fill="#000" font-size="14" textLength="14">ABC</text>
+<text                         y="75" fill="#000" font-size="14" textLength="14">ABC</text>
+</svg>