[merge request] viewport cleanup and doc.

[Teika Kazura <teika lavabit com>]

Hi. The last merge request for 1.6:

* Viewport cleanup: renamed 'viewport-offset-pixel' to
  'viewport-offset-coord'. 'window-relative-position' is unified to
  'window-absolute-position'. These two functions are similar, but not
  identical. The former is recently introduced, so I chose to make the
  old one remain, and merged the newer to the older.

  See the comments in the function, and the related ML thread for more.
* News. libexec -> lib issue and ':user-level' deletion.

Oh, don't ship NEED_DOC* in the 1.6 tarball. Only infinite-desktop
lacks doc at all. Tab in the wiki is almost satisfactory.

Phew, ok, no obstacle seems to remain for 1.6 release.

Regards,
Teika (Teika kazura)