HP-UX needs _HPUX_ALT_XOPEN_SOCKET_API to be defined to be able to
use various POSIX versions of networking functions.  Notably sendmsg()
resulted in "sendmsg() failed (9: Bad file number)" alerts without it.

See xopen_networking(7) for more details.

*) Fixed spelling of "endianness", and called it "byte ordering" in the
   user visible part.

*) Fixed return type of ngx_strerror_init().

*) Fixed a harmless error in spelling of "Connection: close" when computing
   the response header length.

*) Style.

*) Added code to look up Google perftools in /opt/local/, for MacPorts.

*) Resolver: fixed format specification.
   Patch by Yichun Zhang (agentzh).

*) Support for IPv6 literals and an optional port in resolver.

*) Fixed crash in ngx_resolver_cleanup_tree().

   If sending a DNS request fails with an error (e.g., when mistakenly
   trying to send it to a local IP broadcast), such a request is not
   deleted if there are clients waiting on it.  However, it was still
   erroneously removed from the queue.  Later ngx_resolver_cleanup_tree()
   attempted to remove it from the queue again that resulted in a NULL
   pointer dereference.

*) When "resolver" is configured with a domain name, only the first
   resolved address was used.  Now all addresses will be used.

*) Fixed segfault with poll and resolver used.

   Poll event method needs ngx_cycle->files to work, and use of
   ngx_exit_cycle without files set caused null pointer dereference in
   resolver's cleanup on udp socket close.

Fixed compilation with -DNGX_DEBUG_MALLOC on FreeBSD 10.

After jemalloc 3.0.0 import there is no _malloc_options symbol, it has
been replaced with the malloc_conf one with a different syntax.

*) Win32: disallowed access to various non-canonical name variants.

   This includes trailings dots and spaces, NTFS streams (and short names, as
   previously checked).  The checks are now also done in ngx_file_info(), thus
   allowing to use the "try_files" directive to protect external scripts.

*) Win32: normalization of trailing dot inside uri.

   Windows treats "/directory./" identical to "/directory/".  Do the same
   when working on Windows.  Note that the behaviour is different from one
   with last path component (where multiple spaces and dots are ignored by
   Windows).

*) Win32: uris with ":$" are now rejected.

   There are too many problems with special NTFS streams, notably "::$data",
   "::$index_allocation" and ":$i30:$index_allocation".

   For now we don't reject all URIs with ":" like Apache does as there are no
   good reasons seen yet, and there are multiple programs using it in URLs
   (e.g. MediaWiki).

In case of EMFILE/ENFILE returned from accept() we disable accept events,
and (in case of no accept mutex used) arm timer to re-enable them later.
With accept mutex we just drop it, and rely on normal accept mutex handling
to re-enable accept events once it's acquired again.

As we now handle errors in question, logging level was changed to "crit"
(instead of "alert" used for unknown errors).

Note: the code might call ngx_enable_accept_events() multiple times if
there are many listen sockets.  The ngx_enable_accept_events() function was
modified to check if connection is already active (via c->read->active) and
skip it then, thus making multiple calls safe.

Not using full chain passed is ok as consumers are expected to check
event's ready flag to determine if another call is needed, not the
returned size.

We now stop on IOV_MAX iovec entries only if we are going to add new one,
i.e. next buffer can't be coalesced into last iovec.

This also fixes incorrect checks for trailer creation on FreeBSD and
Mac OS X, header.nelts was checked instead of trailer.nelts.

The "complete" flag wasn't cleared on loop iteration start, resulting in
broken behaviour if there were more than IOV_MAX buffers and first
iteration was fully completed (and hence the "complete" flag was set
to 1).

preceding the function.  No functional changes.