Merge pull request #59 from wf49670/develop

Fix problem (kdweeks) where internal page links can overlay footnote hea...
Merge pull request #60 from wf49670/develop

Detect invalid .nf option and fail gracefully. Corrections by wf49670. Thank you Walt.
Merge pull request #61 from wf49670/develop

Fix for interaction issue between page numbers and html literal blocks. Credit: Walt. Thanks.
Include a space before trailing /> of empty HTML elements
Merge pull request #62 from davem2/bugfix-emptyhtmlelementspacing

Include a space before trailing /> of empty HTML elements. Thank you Dave. Looks like I missed a few. Much appreciated.
ensure spacing for illustrations in text
corrected caption text spacing
dospace correction
vertical spacing recode
Fix issue with .di where .il overrides too many <img> elements

If any .il are in the file, ppgen generates CSS for img to set maxwidth to
100% and height to auto. That causes problems for drop-cap images, which
should not be overridden.

This update makes ppgen generate CSS for .figcenter img, .figleft img, or
.figright img instead, as appropriate for the images present in the source
file.