API changes between v0.10 and v0.12

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Buffers

Buffer class has been removed and replaced with a namespace. So using node::Buffer will no longer work.
All node::Buffer::New() variants now return Local<Object> instead of Buffer*.
The return value for node::Buffer::New() is an instantiated JS Buffer object.
node::Buffer::New(Handle<String>) now accepts an optional second argument of enum encoding.
API addition of node::Buffer::Use() which will use the passed char* instead of making a copy.
API addition of node::Crypto::Certificate which handles node::Crypto::Certificate::verifySpkac(Handle<String>), node::Crypto::Certificate::exportPublicKey(Handle<String>) & node::Crypto::Certificte::exportChallenge(Handle<String>) for working naively with SPKAC (Signed public key & challenges) coming from the HTML5 keygen element.

External memory is now allocated using smalloc, instead of using SlowBuffer as the parent backing.
SlowBuffer has been repurposed to return a Buffer instance that has no parent backing.
buffer.parent now points to an object that has been allocated via smalloc.alloc, not a Buffer instance, and only if the buffer is a slice.
buffer.offset is now a read-only prototype property equal to zero since no instance methods require working on the parent backing.
API additions Buffer.alloc() and Buffer.dispose() have been added.
Buffer#fill() has been extended to fill with the entire passed value.
(new Buffer('text\0!', 'ascii')).toString() outputs 'text !' in 0.10 and 'text\u0000!' in 0.12.
Writable stream _write() gets called with 'buffer' encoding when chunk is a Buffer ([#6119](https://github.com/joyent/node/issues/6119)).
Writable stream emits 'finish' on next tick if there was a write() ([#6118](https://github.com/joyent/node/issues/6118)).

process.maxTickDepth has been removed, allowing process.nextTick to starve I/O indefinitely.