get GDK_BUTTON_RELEASE, so move middle button processing ...
(panel_icon_list_button_release): ... here.
* gtkflist.c (gtk_flist_button_release): Open new window if the
middle button is released and DnD is not attempted.
* gscreen.c (panel_chdir): Clear the lists if the chdir operation
was not successful.
* gtkflist.c (gtk_flist_button_press): Only emit the open_row
signal if we are not on the empty area.
* gscreen.c (panel_icon_list_button_press): Ignore double clicks.
(panel_widget_motion): Don't do anything if the button state does
not match the button we are expecting.
* gtkflist.c (gtk_flist_button_press): Remove pending selections
when we receive a double click.
* gaction.c: #include "view.h"
