vty: Add xsd and a command that can generate the documentation.

When building the doxygen documentation do not remove the other
VTY documentation files in the doc/vty folder. Create a command
that can be installed to dump all nodes and commands as XML on
the given VTY. Create a schema for the XML file and a XSL-T script
that can merge the generated file with additional information.
diff --git a/doc/vty/merge_doc.xsl b/doc/vty/merge_doc.xsl
new file mode 100644
index 0000000..6e1bab1
--- /dev/null
+++ b/doc/vty/merge_doc.xsl
@@ -0,0 +1,37 @@
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<xsl:transform version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+                             xmlns:vty="urn:osmocom:xml:libosmocore:vty:doc:1.0">
+  <xsl:output method="xml" version="1.0" encoding="ISO-8859-1" indent="yes" />
+  <xsl:variable name="with" select="'additions.xml'" />
+
+  <xsl:template match="@*|node()">
+    <xsl:copy>
+      <xsl:apply-templates select="@*|node()" />
+    </xsl:copy>
+  </xsl:template>
+
+
+  <!-- Copy the name of the node -->
+  <xsl:template match="vty:node">
+    <xsl:copy>
+      <xsl:apply-templates select="@*|node()" />
+      <xsl:variable name="info" select="document($with)/vty:vtydoc/vty:node[@id=current()/@id]/." />
+      <xsl:for-each select="$info/vty:name">
+          <xsl:copy-of select="." />
+      </xsl:for-each>
+    </xsl:copy>
+  </xsl:template>
+
+
+  <!-- Copy command and add nodes -->
+  <xsl:template match="vty:command">
+    <xsl:copy>
+      <xsl:apply-templates select="@*|node()" />
+      <xsl:variable name="info" select="document($with)/vty:vtydoc/vty:node[@id=current()/../@id]/vty:command[@id=current()/@id]/." />
+      <xsl:for-each select="$info/*">
+          <xsl:copy-of select="." />
+      </xsl:for-each>
+    </xsl:copy>
+  </xsl:template>
+</xsl:transform>
+