Merge pull request #1136 from mathjax/fix/mml3_issue

Fixes the Dutch longdiv issue

Author: zorkow

ts/input/mathml/mml3/mml3.ts

@@ -683,12 +683,12 @@ Mml3.XSLT = `
       <xsl:copy-of select="*[2]"/>
      </m:msrow>
     </xsl:when>
-    <xsl:when test="@longdivstyle='left/\right'">
+    <xsl:when test="@longdivstyle='left/\\right'">
      <m:msrow>
       <m:mrow><xsl:copy-of select="*[1]"/></m:mrow>
       <m:mo>/</m:mo>
       <xsl:copy-of select="*[3]"/>
-      <m:mo>\</m:mo>
+      <m:mo>\\</m:mo>
       <xsl:copy-of select="*[2]"/>
      </m:msrow>
     </xsl:when>