Updated several VCS packages, esp. mupdf

  * mupdf: added desktop and xpm files (removed from upstream, do we
    need them?), changed pkgver function, now it uses number of commit
    from last stable release (that number is hard-coded into PKGBUILD,
    it is cumbersome to maintain PKGBUILD that way but more predictible);

Signed-off-by: Vladimir Lomov <lomov.vl@gmail.com>