$OFF_SITE_LINK_ICON: Don't define here; simply defining it overrides a

definition provided by previously loaded configuration code, and
        testing whether it's defined isn't needed since the default was
        false anyway.

get_link_icon():  Add support for $OFF_SITE_LINK_ICON_HEIGHT and
        $OFF_SITE_LINK_ICON_WIDTH, giving the dimensions of the icon
        being used.  This can make for faster page display.  Both are
        optional.

make_my_titlegraphic():  Fix insertion of the off-site icon link.

do_env_funcdesc():  Remove debugging print.

handle_rfclike_reference():  Remove trailing colon from first line; it
        doesn't really make sense and looks bad if we add an icon to
        mark off-site links.