Fixed handling of very long locations (ticket #2435). Previously, location prefix length in ngx_http_location_tree_node_t was stored as "u_char", and therefore location prefixes longer than 255 bytes were handled incorrectly. Fix is to use "u_short" instead. With "u_short", prefixes up to 65535 bytes can be safely used, and this isn't reachable due to NGX_CONF_BUFFER, which is 4096 bytes.