This commit makes a few improvements in default bindings:
* use chm_http text-mode handler for CHM files;
* play sounds only from videos in text mode;
* use pdftotext -layout -nopgbrk switches;
* try to use elinks before links for HTML;
* soffice2html text-mode handler for SXW files;
* wvHtml text-mode handler for doc files;
* xlhtml text-mode handler for XLS files;
* ppthtml text-mode handler for PPT/PPS files;
* open=view+pager fallback (noX) for PostScript, PDF, OD[PST] and DVI;
* standarized $DISPLAY checks.
Signed-off-by: Slava Zanko <slavazanko@gmail.com>
