fs: fix fs.truncate() file content zeroing bug

fs.truncate() and its synchronous sibling are implemented in terms of
open() + ftruncate().  Unfortunately, it opened the target file with
mode 'w' a.k.a. 'write-only and create or truncate at open'.

The subsequent call to ftruncate() then moved the end-of-file pointer
from zero to the requested offset with the net result of a file that's
neatly truncated at the right offset and filled with zero bytes only.

This bug was introduced in commit 168a5557 but in fairness, before that
commit fs.truncate() worked like fs.ftruncate() so it seems we've never
had a working fs.truncate() until now.

Fixes #6233.
dtrace: backport two byte string fix

This is a partial backport of 5921158

Re #6309
Closes #6319
tls: fix premature connection termination

Destroying the TLS session implies destroying the underlying socket but
before this commit, that was done with net.Socket#destroy() rather than
net.Socket#destroySoon().  The former closes the connection right away,
even when there is still data to write.  In other words, sometimes the
final TLS record got truncated.

Fixes #6107.
blog: Remove wp-to-markdown script
doc: addon: fix object instantiation examples

* Extend examples to show how to handle non-constructor invocation in
  constructor callback functions.

* Fix up examples to initialize member variables at object construction.

* Fix up a few naming inconsistencies.

Fixes #5701.
doc: net: remove bad net.Server description

net.Server is not an instance of net.Socket so don't say it is.
test: use proper findjsobjects output format

Closes #6329
doc: document os.loadavg() behavior on windows

The load average is a very UNIX-y concept.  That's why os.loadavg()
always returns zeros on Windows.  Mention that in the documentation.
doc: expand os.loadavg() section

Add a short explanation of what the load average is and why it's
unavailable on Windows.

Also sneak in a fix for a typo that I introduced in commit 56c5806.
doc: http: add cross-links for easier clicking

Make it a little easier to navigate the http module documentation by
turning class names and methods into links to the appropriate section.
doc: http: reword IncomingMessage 'close' event

The bit that says "before response.end() was called or able to flush"
doesn't apply to incoming streams.

Fixes #6359.
doc: child_process corrections and cleanups

- Make explicit that .disconnected is set before the disconnect event,
  and it is not allowed to send messages after calling .disconnect(),
  even while waiting for a delayed disconect event.
- Remove obsolete claim that explicit exit is required
- Describe silent: in the options for fork()
- Describe .connected as the property it is, not just as an aside in
  the disconnect() method
doc: cluster documentation cleanup and corrections

- fixed some incomprehensible wording ("event assigned to..."?)
- removed undocumented and unnecessary process properties from example
- corrected the docs on the default for the exec setting
- described when workers are removed from cluster.workers
- described addressType, which was documented as existing, but not what
  values it might have
- spell out more clearly the limitations of setupMaster
- describe disconnect in sufficient detail that why a child does or does
  not exit can be understood
- clarify which cluster functions and events are available on process or
  just on the worker, as well as which are not available in children,
- don't describe events as the same, when they have receive different
  arguments
- fix misleading disconnect example: since disconnect already calls
  close on all servers, doing it again in the example is a no-op, not
  the "force close" it was claimed to be
- document the error event, not catching it will kill your node
- describe suicide better, it is important, and a bit unintuitive
  (process.exit() is not suicide?)
- use worker consistently throughout, instead of child.
http_parser: expose pause/resume method for parser
http: provide backpressure for pipeline flood

If a client sends a lot more pipelined requests than we can handle, then
we need to provide backpressure so that the client knows to back off.
Do this by pausing both the stream and the parser itself when the
responses are not being read by the downstream client.

Backport of 085dd30
uv: Upgrade to v0.10.18
crypto: clear errors from verify failure

OpenSSL will push errors onto the stack when a verify fails, which can
disrupt TLS and other routines if we don't clear the error stack

Fixes #6304
2013.10.18, Version 0.10.21 (Stable)

* uv: Upgrade to v0.10.18

* crypto: clear errors from verify failure (Timothy J Fontaine)

* dtrace: interpret two byte strings (Dave Pacheco)

* fs: fix fs.truncate() file content zeroing bug (Ben Noordhuis)

* http: provide backpressure for pipeline flood (isaacs)

* tls: fix premature connection termination (Ben Noordhuis)
Merge branch 'v0.10.21-release' into v0.10
Now working on 0.10.22