After a stream was unpiped there would stil be residual event handlers

Fix a bug where calling .end() on a socket without calling .connect() first
throws a TypeError:

  TypeError: Cannot read property 'shutdown' of undefined
      at Socket.onSocketFinish (net.js:194:20)
      at Socket.EventEmitter.emit (events.js:91:17)
      at Socket.Writable.end (_stream_writable.js:281:10)
      at Socket.end (net.js:352:31)

Fixes #4463.

Remove obsolete build configuration that escaped the purge in 7eaea7f9.

When building custom `node` versions (e.g., floating features/fixes from
different versions) it's often useful to specify a custom tag which
easily identifies build when invoking `node -v`.

Introduce a way to specify this tag in `node_version.h` file or by
running `./configure --tag="<tag>"`. Insert it right after the patch
version (and before `-pre`, if build is not a release).

Closes #4452.

* streams: Update all streaming interfaces to use new classes (isaacs)

* node: remove idle gc (Ben Noordhuis)

* http: protect against response splitting attacks (Bert Belder)

* fs: Raise error when null bytes detected in paths (isaacs)

* fs: fix 'object is not a function' callback errors (Ben Noordhuis)

* fs: add autoClose=true option to fs.createReadStream (Farid Neshat)

* process: add getgroups(), setgroups(), initgroups() (Ben Noordhuis)

* openssl: optimized asm code on x86 and x64 (Bert Belder)

* crypto: fix leak in GetPeerCertificate (Fedor Indutny)

* add systemtap support (Jan Wynholds)

* windows: add ETW and PerfCounters support (Scott Blomquist)

* windows: fix normalization of UNC paths (Bert Belder)

* crypto: fix ssl error handling (Sergey Kholodilov)

* node: remove eio-emul.h (Ben Noordhuis)

* os: add os.endianness() function (Nathan Rajlich)

* readline: don't emit "line" events with a trailing 'n' char (Nathan Rajlich)

* build: add configure option to generate xcode build files (Timothy J Fontaine)

* build: allow linking against system libuv, cares, http_parser (Stephen Gallagher)

* typed arrays: add slice() support to ArrayBuffer (Anthony Pesch)

* debugger: exit and kill child on SIGTERM or SIGHUP (Fedor Indutny)

* url: url.format escapes delimiters in path and query (J. Lee Coltrane)

Fixes #3226.

Consider a production server that uses a REPL to debug. Creating the instance
would wipe out the global cache of modules, and subsequent "require" calls in
the server would be reloaded from disk. The REPL should observe only, without
altering, its environment.

Starting a line with `**bold**` text makes it think that it's a link,
and get confused.

This should really be fixed properly in the doc generator, but for now,
it's not a major issue.  It's probably just a matter of updating marked.

This fixes windows stdio pipes in streams2 land.

It used to be off before. It's extremely unlikely that such an attack
would be a viable attack against node. And it makes AES much slower.

When perlasm generates MASM code it sets the assembler target to 468.
In this mode MASM refuses to assemble a couple of instructions. Bumping
the target to 686 solves this problem.

This patch brings the openssl library that is built with gyp closer
to what the standard build system produces.

All opensslconf.h versions are now merged into a single file, which
makes it easier for compiled addons to locate this file.

Apply the same optimization to res.end(buf) that is applied to res.end(str).

Speeds up `node benchmark/http_simple_auto -k -c 1 -n 25000 buffer/1`
(non-chunked response body) by about 750x. That's not a typo.

Chunked responses:

  $ cat tmp/http-chunked-client.js
  // Run `node benchmark/http_simple` in another terminal.
  var http = require('http'), url = require('url');
  var options = url.parse('http://127.0.0.1:8000/buffer/1/1');
  options.agent = new http.Agent({ maxSockets: 1 });
  for (var i = 0; i < 25000; ++i) http.get(options);

Before:

  $ time out/Release/node tmp/http-chunked-client.js
  real    16m40.411s
  user    0m9.184s
  sys     0m0.604s

After:

  $ time out/Release/node tmp/http-chunked-client.js
  real    0m5.386s
  user    0m2.768s
  sys     0m0.728s

That's still a 185x speed-up.

Fixes #4415.

Use res.end() for the final chunk so we can benchmark the 'hot path' shortcut
in lib/http.js that packs the headers and the body into a single packet.

This fixes pummel/test-net-write-callbacks