With this change all such frames will be added in front of the output queue, and
will be sent first.  It prevents HOL blocking when response with higher priority
is blocked by response with lower priority in the middle of the queue because
the order of their SYN_REPLY frames cannot be changed.

Proposed by Yury Kirpichev.

While ngx_http_spdy_write_handler() should not make any harm with current code,
calling it during finalization of SPDY connection was not intended.

If an error occurs in a SPDY connection, the c->error flag is set on every fake
request connection, and its read or write event handler is called, in order to
finalize it.  But while waiting for request headers, it was a no-op since the
read event handler had been set to ngx_http_empty_handler().

If an error occurs in a SPDY connection, the c->error flag is set on every fake
request connection, and its read or write event handler is called, in order to
finalize it.  But while waiting for a request body, it was a no-op since the
read event handler ngx_http_request_handler() calls r->read_event_handler that
had been set to ngx_http_block_reading().

This was missed in 9d59a8eda373 when non-buffered support was added to SCGI
and uwsgi.

With previous code only part of u->buffer might be emptied in case
of special responses, resulting in partial responses seen by SSI set
in case of simple protocols, or spurious errors like "upstream sent
invalid chunked response" in case of complex ones.

Signed-off-by: Piotr Sikora <piotr@cloudflare.com>

Location tree was always constructed using case-sensitive comparison, even
on case-insensitive systems.  This resulted in incorrect operation if
uppercase letters were used in location directives.  Notably, the
following config:

    location /a { ... }
    location /B { ... }

failed to properly map requests to "/B" into "location /B".