Accept -1 len in rest_xml_parser_parse_from_data
Accept -1 len in rest_xml_parser_parse_from_data

This means that the passed in string is nul-terminated and that
rest_xml_parser_parse_from_data should get its length with strlen.

https://bugzilla.gnome.org/show_bug.cgi?id=657032

GNOME/librest,Distrotech/librest,GNOME/librest,GNOME/librest,Distrotech/librest