Introduced a new Doxygen XML tag '<docref>'. The intention of
this tag is to indicate a section of text in the Doxygen XML that
will contain a reference to another section in the Manual e.g.
"See \autoref<sec:x>". As other generation formats aren't aware of
other chapters/sections in the manual, the <docref> encapsulation
allows it to omit the text from the output. The Latex generator
has been modified to continue parsing the 'docref' contents.