- \forward_search_dvi and \forward_search_pdf RC settings.
- By default, the value for pdf is empty, while for dvi it is\n
- "xdvi -sourceposition $$n:$$t $$o"\n
- The values replaced in the call: $$n for row number, $$t for
- exported temporary .tex file, $$o exported output file, either
- dvi or pdf, depending on which one exists in the temp dir
- (preferred is dvi).