Job.build_html(): Be more robust in ensuring about.html exists; copying

    the right HTML file to the name about.html is needed even if the
    --numeric option was not given -- some other name may have been
    assigned due to some non-determinism in the algorithm use to perform
    name allocation.  ;-(

This closes the "About..." portion of SF bug #420216.

Doc/tools/mkhowto

@@ -369,7 +369,6 @@ class Job:
         shutil.copyfile(os.path.join(builddir, self.doc + ".html"),
                         os.path.join(builddir, "index.html"))
         if max_split_depth != 1:
-            if self.options.numeric:
             label_file = os.path.join(builddir, "labels.pl")
             fp = open(label_file)
             about_node = None
@@ -386,7 +385,7 @@ class Job:
                     shutil.copyfile(os.path.join(builddir, about_node),
                                     os.path.join(builddir, "about.html"))
                     break
-            else:
+            if not self.options.numeric:
                 pwd = os.getcwd()
                 try:
                     os.chdir(builddir)