tls: stop NodeBIO::Gets from reading off end of buffer

NodeBIO::Gets was reading off the end of a buffer if it
didn't find a "\n" before the EOF.  This behavior
was causing X509 certificates passed to `https.Agent`
via the "ca" option to be silently discarded. It also
was causing improper parsing of certs and keys
passed to https.Agent, but those problems were worked
around in cdde9a3.

Backed out workaround in `lib/crypto.js` from ccde9a3,
which now isn't needed.  But keep the test introduced
in that commit, which tests properly for this
bug.

This bug was first introduced in a58f93f

Gist containing test code, bisection log, and notes:
   https://gist.github.com/maxtaco/9211605
test: remove invalid part of stream2-stderr-sync

One test case in test-stream2-stderr-sync.js was creating a TTY
object using an undocumented constructor and passing in fd 2.
However, this is running in a child process and fd 2 is actually
a pipe, not a TTY.

The constructor fails on Windows and causes the handle type to be
left uninitialized, which later causes an assert to fail.

On Unix, the constructor fails to retrieve the windows size but unlike
on Windows, it just leaves the size fields undefined and continues
with initializing the stream type, yielding a semi-usable object.

I could make the Windows version match Unix behavior, but it
seems to me that the test is relying on an implementation detail of
an undocumented API, and the Unix behavior is not necessarily more
correct than the Windows one. Thus it makes more sense to remove this
test.
src: make stdout/sterr pipes blocking

Expose `setBlocking` on Pipe's and if a pipe is being created for stdio
on windows then make the pipes blocking.

This fixes test-stream2-stderr-sync.js on Windows.

Fixes #3584
test: fix async-listener-run-error-once

Rely on defined order of operations by closing the server and
destorying the client socket, instead of when setImmediate fires
test: add failing http `agent: null` test

See #7012.
http, https: don't depend on `globalAgent`

For the `request()` and `get()` functions. I could never
really understand why these two functions go through agent
first... Especially since the user could be passing `agent: false`
or a different Agent instance completely, in which `globalAgent`
will be completely bypassed.

Moved the relevant logic from `Agent#request()` into the
`ClientRequest` constructor.

Incidentally, this commit fixes #7012 (which was the original
intent of this commit).
test: update "http-*" tests to only use public API

Don't invoke the `agent.requst()` or `agent.get()` functions
directly. Instead, use the public API and pass the agent
instance in as the `agent` option.
http: remove the circular dependency

Between `ClientRequest` and `Agent`. The circular require was doing
weird things at load time, like making the `globalAgent` property
be `undefined` from within the context of the "_http_client"
module.

Removing the circular dependency completely fixes this.

This commit effectively removes the undocumented `Agent#request()`
and `Agent#get()` functions.