Core: allow strings without null-termination in ngx_parse_url(). This fixes buffer over-read while using variables in the "proxy_pass", "fastcgi_pass", "scgi_pass", and "uwsgi_pass" directives, where result of string evaluation isn't null-terminated. Found with MemorySanitizer. Signed-off-by: Piotr Sikora <piotrsikora@google.com>