Section head link targets not generated in manual

[bergey]

Links to section headings in the user manual are not working. The links are fine, with the expected #the-transformable-class form. The anchor tags which should be the targets of those links are not present. Examples:

http://projects.haskell.org/diagrams/doc/manual.html#the-transformable-class
http://projects.haskell.org/diagrams/doc/manual.html#deformations