get_header_value(), get_header_value_u64(), get_multimap_value() and
MultipartFormData::get_field() advanced an equal_range() iterator by
the caller's index after casting it to ssize_t. An index that is
negative as a signed value stepped back onto an entry of another key,
and a huge positive one kept looping after the last match.
Advance with bounded_next(), which stops at the end of the range.
yhirose
11daa99c86
