SPDY: fix support for headers with multiple values. Split SPDY header with multiple, NULL-separated values: cookie: foo\0bar into two separate HTTP headers with the same name: cookie: foo cookie: bar Even though the logic for this behavior already existed in the source code, it doesn't look that it ever worked and SPDY streams with such headers were simply rejected. Signed-off-by: Piotr Sikora <piotr@cloudflare.com>