doc: document that stdio is usually blocking
crypto: check randomBytes() size argument

Throw a TypeError if size > 0x3fffffff. Avoids the following V8 fatal
error:

  FATAL ERROR: v8::Object::SetIndexedPropertiesToExternalArrayData()
  length exceeds max acceptable value

Fixes #5126.
v8: Unify kMaxArguments with number of bits used to encode it.

Increase the number of bits by 1 by making Flags unsigned.

BUG=chromium:211741

Review URL: https://chromiumcodereview.appspot.com/12886008

This is a back-port of commits 13964 and 13988 addressing CVE-2013-2632.
tls: remove harmful unnecessary bounds checking

The EncIn, EncOut, ClearIn & ClearOut functions are victims of some code
copy + pasting. A common line copied to all of them is:

`if (off >= buffer_length) { ...`

448e0f43 corrected ClearIn's check from `>=` to `>`, but left the others
unchanged (with an incorrect bounds check). However, if you look down at
the next very next bounds check you'll see:

`if (off + len > buffer_length) { ...`

So the check is actually obviated by the next line, and should be
removed.

This fixes an issue where writing a zero-length buffer to an encrypted
pair's *encrypted* stream you would get a crash.
test: Make child-process-fork-getconnections noisier

Easier to tell what's going on, and observe the weird behavior on
Darwin, where sockets are apparently getting FIN'd before we FIN them.
debugging: Add absurd logging in UV stream.c