Fix issue where .pn statements inside .nf blocks result in leading space miscalculation

Hi Roger,

While working on the index section of my latest PP project, I noticed a minor bug. Within an .nf block, leading spaces are not set properly for lines which follow a .pn statement (HTML output only).

[This file](https://dl.dropboxusercontent.com/u/59728548/test-src.txt) demonstrates the issue (notice how the lines which immediately follow .pn statements are not indented properly)

The code related to this was already accounting for inline style \</> markup, this fix checks for page number markup as well.

David