Changelog:
* Add --xinerama-index option for background setting (patch by James Knight)
* When removing the last image in slidsehow mode, stay on the last
(previously second-to-last) image (patch by Lior Shiponi)
* Allow --sort and --randomize to override each other (most recently
specified option wins) instead of always preferring --sort
* Thumbnail mode: Mark image as processed when executing an action
(--action) by clicking on an image
* It is now possible to override feh's idea of the active xinerama screen
using the --xinerama-index option
* Remove (undocumented) feature allowing to override feh's idea of the
active xinerama screen by setting the XINERAMA_SCREEN environment variable
