Implemented cross-references to list items ...

• Added label attribute to <item> element.
• Added cross-referencing to <item> labels.

Note this only makes sense for enumerated lists, but this isn’t checked
as there’s no clean way to do it. There’s also no check that the <item>
is inside a list element, because there are about a billion different
element variants that can be used to specify a list.

• Fixed definition lists so that standalone <term> elements aren’t converted into list items.

• Switched to XPath value comparison operators (eq, etc.) where appropriate. ...

• Made better use of XPath general comparison operators for lists of alternatives.
• Normalised synonyms for “center” in attributes.
• Normalised synonyms for “yes” and “no” in attributes.

• Moved processing of \item[] for definition lists into the keyword element. ...

• Added @linebreak attribute for definition list keywords.

• Corrected generation of value attributes for enumerated <li> elements in (X)HTML.

Fixed permissions.

- Reformatted code and made consistent use of xsl:text and newline-internal. ...

- Added the various list elements to the collection of "paragraph-like" elements
  that shouldn't have <p></p> wrapped around them.

- Shifted list processing elements into a separate module.