Perform actions on thumbnails.

Because otherwise the examples directory also gets 644.

Only if a previously selected item (mouse over, keyboard) is available
though.

Squashed commit of the following:

commit 55e66e15af898f4c01d7d265013124fefce795e4
Author: Daniel Friesel <derf@finalrewind.org>
Date:   Mon Sep 26 19:59:46 2011 +0200

    Save all filenames in ~/.fehbg

commit afc2774f315fc379aa96de58decf8370772036af
Author: Daniel Friesel <derf@finalrewind.org>
Date:   Mon Sep 26 19:24:38 2011 +0200

    Update test/bg --bg-fill images (off-by-one due to changed implementation)

commit bd4210cff2e895414df12868f6cab7f193c5adf5
Author: Daniel Friesel <derf@finalrewind.org>
Date:   Mon Sep 26 14:47:00 2011 +0200

    Fix feh_wm_set_bg_maxed

commit d9ada9dc2a74aef6ae0924e9c0ff296b94ee25bc
Author: Daniel Friesel <derf@finalrewind.org>
Date:   Mon Sep 26 14:39:11 2011 +0200

    Fix for non-xinerama setups

commit be2cf0f1f8c00b737e7141a372d3cbc9db4c949f
Author: Daniel Friesel <derf@finalrewind.org>
Date:   Mon Sep 26 14:24:44 2011 +0200

    Move wallpaper calculation code into separate functions

commit 4e07c1f9734569fdd778a813c5a85c63b51b3175
Author: Daniel Friesel <derf@finalrewind.org>
Date:   Mon Sep 26 13:01:46 2011 +0200

    Remove unnecessary temporary variable

commit 23d1d733b21d1560e1fbcadddc34cae3d666b21d
Author: Daniel Friesel <derf@finalrewind.org>
Date:   Mon Sep 26 12:46:25 2011 +0200

    Initial conversion, works with --bg-scale

This fixes a "memory leak" (though strictly speaking it is none) when using
feh --reload on http URLs.

This was broken by the changes allowing --reload to retry ad infinitum.

Now force_new is used to decide whether or not to work around the Imlib2
caching issue.  Because of this, a few feh_reload_image calls needed to be
changed.