Updated docs

  * emacs/emacs.org: fixed wrong var. name (missed 's') for agenda
    configuration, removed old 'diary' from agenda (use Org featured
    'diary.org');
  * openbox/autostart.org: use 'compton' instead of 'xcompmgr';
  * regenerate (tangled from Org documents) files:
    - (TOP)/emacs.d/org-us.el;
    - (TOP)/openbox/autostart;
    - (TOP)/feh/fehbg.

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