Fix warning during manpage generaton

> ERROR: xref linking to Stubs has no generated link text.
> Error: no ID for constraint linkend: Stubs.

(Despite saying "ERROR", this is actually a warning, and manpages are
still generated)

Improve chapter-texi2docbook so it generates elements for texinfo
sections as well, so that a cross-reference to the "Stubs" section
contains a valid element ID.

newlib/doc/chapter-texi2docbook.py

@@ -14,6 +14,7 @@ import re
 
 def main():
     first_node = True
+    prev_sect = False
 
     print ('<?xml version="1.0" encoding="UTF-8"?>')
     print ('<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">')
@@ -27,18 +28,27 @@ def main():
         if l.startswith("@node"):
             l = l.replace("@node", "", 1)
             l = l.strip()
-            l = l.lower()
             if first_node:
-                print ('<chapter id="%s_chapter" xmlns:xi="http://www.w3.org/2001/XInclude">' % l.replace(' ', '_'))
+                print ('<chapter id="%s_chapter" xmlns:xi="http://www.w3.org/2001/XInclude">' % l.lower().replace(' ', '_'))
                 first_node = False
+            else:
+                if prev_sect:
+                    print ('</section>')
+                print ('<section id="%s">' % l)
+                prev_sect = True
         elif l.startswith("@chapter "):
             l = l.replace("@chapter ", "", 1)
             print ('<title>%s</title>' % l)
+        elif l.startswith("@section "):
+            l = l.replace("@section ", "", 1)
+            print ('<title>%s</title>' % l)
         elif l.startswith("@include "):
             l = l.replace("@include ", "", 1)
             l = l.replace(".def", ".xml", 1)
             print ('<xi:include href="%s"/>' % l.strip())
 
+    if prev_sect:
+        print ('</section>')
     print ('</chapter>')
 
 if __name__ == "__main__" :