Peforms a Synctex backward search to obtain the TeX input file, line and
(possibly) column corresponding to the position (@x,@y) (in 72dpi
coordinates) in the @page of @document.
A pointer to the EvSourceLink structure that holds the result. @NULL if synctex
is not enabled for the document or no result is found.
The EvSourceLink pointer should be freed with g_free after it is used.
Peforms a Synctex backward search to obtain the TeX input file, line and (possibly) column corresponding to the position (@x,@y) (in 72dpi coordinates) in the @page of @document.