GitLab

(Fprevious_char_property_change): allow marker as limit.
(Fnext_single_char_property_change)
(Fprevious_single_char_property_change): Check that limit is a
number in strings.
(Fnext_single_char_property_change): Coerce position to integer.
(Fprevious_single_char_property_change): Same here.