Improve compatibility with TOCMacro and TracNumberedHeadlinesPlugin.

[anonymous]

Currently, "first level" headings/headlines appear to be excluded from TOC if they do not have sub-headings or sub-headlines.

For example, the following is defined:

#Section 1#
blah blah section 1!

#Section 2#
##Background##
blah blah section 2 background.

##Conclusion##
blah blah seciton 2 conclusion.

Then the following TOC is generated:

2.1 Background
2.2 Conclusion

rather than

1. Section 1
2. Section 2
2.1 Background
2.2 Conclusion