It was working for nginx's own 206 replies as they are seen as 200 in the
headers filter module (range filter goes later in the headers filter chain),
but not for proxied replies.

Additional parsing logic added to correctly handle RFC 3986 compliant IPv6 and
IPvFuture characters enclosed in square brackets.

The host validation was completely rewritten. The behavior for non IP literals
was changed in a more proper and safer way:

 - Host part is now delimited either by the first colon or by the end of string
   if there's no colon. Previously the last colon was used as delimiter which
   allowed substitution of a port number in the $host variable.
   (e.g. Host: 127.0.0.1:9000:80)

 - Fixed stripping of the ending dot in the Host header when the host was also
   followed by a port number.
   (e.g. Host: nginx.com.:80)

 - Fixed upper case characters detection. Previously it was broken which led to
   wasting memory and CPU.

Non-default servers may not have ssl context created if there are no
certificate defined.  Make sure to check if ssl context present before
using it.

Patch by Alexander Usov.  The bug has been introduced in r4267.

Check if received data length match Content-Length header (if present),
don't cache response if no match found.  This prevents caching of corrupted
response in case of premature connection close by upstream.

Used "\x5" in 5th byte to claim presence of both audio and video.  Used
previous tag size 0 in the beginning of the flv body (bytes 10 .. 13) as
required by specification (see http://www.adobe.com/devnet/f4v.html).

Patch by Piotr Sikora.