Fix for issue #49 (FF page number interaction with drop-caps)

Detect a pageno span immediately after a <p for a drop-cap, and move it
to before the <p. This will leave the pageno naked, but ppgen will detect
that and put a <div> around it.
Merge pull request #50 from wf49670/FFpageno

Fix for issue #49 (FF page number interaction with drop-caps). Thank you Walt.