Cache: removed dead store in ngx_http_file_cache_vary_header().

Found by Clang Static Analyzer.
SPDY: fixed "too long header line" logging.

This fixes possible one byte buffer overrun and makes sure ellipsis are
always added, see 21043ce2a005.
Upstream: add "proxy_ssl_certificate" and friends.

Signed-off-by: Piotr Sikora <piotr@cloudflare.com>
Upstream: support named location for X-Accel-Redirect.