Signed-off-by: Daniel Friesel <derf@finalrewind.org>

When executing an action starting with a semicolon, feh will
not skip to the next slide. The semicolon is not passed on to
the executing shell, of course. This is kinda ugly, but at least
it makes action handling somewhat more flexible.

Option --action-hold-slide. If specified, when in slideshow mode images will not automatically change after running user action. Otherwise, slideshow images will cycle after action as usual.

1) winwidget.c winwidget.h New function winwidget_update_caption using code in winwindget_render_image. This code was removed from the latter, and replaced with a call to winwidget_update_caption.

2) Image caption is updated after running action when in slideshow mode.
3) Running action in slideshow mode no longer changes the image automatically.