This commit removes the feh_file_remove_from_list call from feh_reload_image.
We can safely do this because if the file itself was removed, cb_reload_timer
will take care of updating the filelist, and in all other cases it is intended
to leave the image in the filelist and retry.

A warning will be displayed in the image if the reload failed.

Note that read_filelist used to check if its argument was an image (for people
accidentaly typing "feh -df *" instead of "feh -dF *"); this was removed
because it failed on /dev/stdin.

I might re-add it, but I'm not yet sure about the future of feh's automatic
filelist saving.

It is pretty random and I doubt anyone actually uses it. Also, after removing
it, there are only two duplicates of the image index code instead of three...