SPDY: ngx_http_spdy_state_headers() error handling cleanup.
SPDY: ngx_http_spdy_state_headers() error handling cleanup.

 - Specification-friendly handling of invalid header block or special headers.
   Such errors are not fatal for session and shouldn't lead to connection close;

 - Avoid mix of NGX_HTTP_PARSE_INVALID_REQUEST/NGX_HTTP_PARSE_INVALID_HEADER.

hy0kl/nginx,firebase/nginx,hy0kl/nginx,firebase/nginx,firebase/nginx,firebase/nginx,hy0kl/nginx