doc: don't suggest to reuse net.Socket objects

Using Socket.prototype.connect() to reconnect an existing Socket object
is not reliable. Users should just create a new Socket object.

See #4698.
zlib: reduce memory consumption, release early

In zlibBuffer(), don't wait for the garbage collector to reclaim the zlib memory
but release it manually. Reduces memory consumption by a factor of 10 or more
with some workloads.

Test case:

  function f() {
    require('zlib').deflate('xxx', g);
  }
  function g() {
    setTimeout(f, 5);
  }
  f();

Observe RSS memory usage with and without this commit. After 10,000 iterations,
RSS stabilizes at ~35 MB with this commit. Without, RSS is over 300 MB and keeps
growing.

Cause: whenever the JS object heap hits the high-water mark, the V8 GC sweeps
it clean, then tries to grow it in order to avoid more sweeps in the near
future. Rule of thumb: the bigger the JS heap, the lazier the GC can be.

A side effect of a bigger heap is that objects now live longer. This is harmless
in general but it affects zlib context objects because those are tied to large
buffers that live outside the JS heap, on the order of 16K per context object.

Ergo, don't wait for the GC to reclaim the memory - it may take a long time.

Fixes #4172.
zlib: pass object size hint to V8

Inform V8 that the zlib context object is tied to a large off-heap buffer.

This makes the GC run more often (in theory) and improves the accuracy of
--trace_external_memory.
blog: remove dangling symlink

Fixes #4716.
npm: Upgrade to v1.2.10
2013.02.06, Version 0.8.19 (Stable)

* npm: Upgrade to v1.2.10

* zlib: pass object size hint to V8 (Ben Noordhuis)

* zlib: reduce memory consumption, release early (Ben Noordhuis)

* buffer: slow buffer copy compatibility fix (Trevor Norris)

* zlib: don't assert on malformed dictionary (Ben Noordhuis)

* zlib: don't assert on missing dictionary (Ben Noordhuis)

* windows: better ipv6 support (Bert Belder)

* windows: add error mappings related to unsupported protocols (Bert Belder)

* windows: map ERROR_DIRECTORY to UV_ENOENT (Bert Belder)
Merge branch 'v0.8.19-release' into v0.8
Now working on 0.8.20
blog: v0.8.19 release
http: protect against response splitting attacks

This patch is a back-port of 3c293ba.
Closes #4696
blog: v0.9.9
blog: v0.9.9 is unstable, not stable
test: disable simple/test-dgram-send-error

It's not a good citizen, it spams random IP addresses with UDP packets.

Fixes #4730.