remove r->zero_in_uri

cache related fixes:

*) do not cache response if it has "no-store" or "private"
   in "Cache-Control" header
*) proxy_no_cache and fastcgi_no_cache

use lstat() for WebDAV DELETE, COPY, and MOVE to handle symlinks

opening files fixes:

*) use non-blocking open() not to hang on FIFO files, etc.
*) do not log misleading errno in "not a regular file" error

rewrite fixes:

*) escape ampersand in argument while rewrite
*) autodetect redirect if URI is rewritten to a string starting with $scheme

revert partially r1555 and fix the error "memcached sent invalid trailer"

reset a parsing state to parse correctly an upstream response,
if 400 or 414 response has been redirected to upstream

*) make $request_method non-cacheable
*) make $arg_ variables non-cacheable
*) change processing variables accessed by SSI and perl module:
   *) the indexed variables are always flushed
   *) never show warning for not found variables

allow HTTPS referers