[PATCH] Fix issue 1011

[Christian Hitz]

Hi,

the following patchset fixes issue 1011.

In order to verify the fix I have added a new regression test suite 
lilypondbook_html. It tests the lilypond-book operation when processing HTML 
files. Most of the patch is related to this regression test.

http://codereview.appspot.com/206092/show

Note: Rietveld insists on squashing my Git commits. I'll provide a set of 
patches when the changes are ready to be pushed.

Regards,
Christian