This makes it possible to avoid looping for a long time while working
with a fast enough peer when data are added to the socket buffer faster
than we are able to read and process them (ticket #1431).  This is
basically what we already do on FreeBSD with kqueue, where information
about the number of bytes in the socket buffer is returned by
the kevent() call.

With other event methods rev->available is now set to -1 when the socket
is ready for reading.  Later in ngx_recv() and ngx_recv_chain(), if
full buffer is received, real number of bytes in the socket buffer is
retrieved using ioctl(FIONREAD).  Reading more than this number of bytes
ensures that even with edge-triggered event methods the event will be
triggered again, so it is safe to stop processing of the socket and
switch to other connections.

Using ioctl(FIONREAD) only after reading a full buffer is an optimization.
With this approach we only call ioctl(FIONREAD) when there are at least
two recv()/readv() calls.

WSAPoll() is only available with Windows Vista and newer (and only
available during compilation if _WIN32_WINNT >= 0x0600).  To make
sure the code works with Windows XP, we do not redefine _WIN32_WINNT,
but instead load WSAPoll() dynamically if it is not available during
compilation.

Also, sockets are not guaranteed to be small integers on Windows.
So an index array is used instead of NGX_USE_FD_EVENT to map
events to connections.

Resolved warnings about declarations that hide previous local declarations.
Warnings about WSASocketA() being deprecated resolved by explicit use of
WSASocketW() instead of WSASocket().  When compiling without IPv6 support,
WinSock deprecated warnings are disabled to allow use of gethostbyname().

    *) Bugfix: nginx did run on Linux parisc.

    *) Feature: nginx now does not start under FreeBSD if the sysctl
       kern.ipc.somaxconn value is too big.

    *) Bugfix: if a request was internally redirected by the
       ngx_http_index_module module to the ngx_http_proxy_module or
       ngx_http_fastcgi_module modules, then the index file was not closed
       after request completion.

    *) Feature: the "proxy_pass" can be used in location with regular
       expression.

    *) Feature: the ngx_http_rewrite_filter_module module supports the
       condition like "if ($HTTP_USER_AGENT ~ MSIE)".

    *) Bugfix: nginx started too slow if the large number of addresses and
       text values were used in the "geo" directive.

    *) Change: a variable name must be declared as "$name" in the "geo"
       directive. The previous variant without "$" is still supported, but
       will be removed soon.

    *) Feature: the "%{VARIABLE}v" logging parameter.

    *) Feature: the "set $name value" directive.

    *) Bugfix: gcc 4.0 compatibility.

    *) Feature: the --with-openssl-opt=OPTIONS autoconfiguration directive.

    *) Bugfix: in the ngx_http_autoindex_module if the long file names were
       in the listing.

    *) Feature: the "^~" modifier in the location directive.

    *) Feature: the proxy_max_temp_file_size directive.

    *) Bugfix: on Solaris and Linux there may be too many "recvmsg()
       returned not enough data" alerts.

    *) Bugfix: there were the "writev() failed (22: Invalid argument)"
       errors on Solaris in proxy mode without sendfile. On other platforms
       that do not support sendfile at all the process got caught in an
       endless loop.

    *) Bugfix: segmentation fault on Solaris in proxy mode and using
       sendfile.

    *) Bugfix: segmentation fault on Solaris.

    *) Bugfix: on-line upgrade did not work on Linux.

    *) Bugfix: the ngx_http_autoindex_module module did not escape the
       spaces, the quotes, and the percent signs in the directory listing.

    *) Change: the decrease of the copy operations.

    *) Feature: the userid_p3p directive.