node: always set function name

For easier debugging it's helpful to always have the function name.
These were not set for methods coming from cc.
smalloc: create separate module

It will be confusing if later on we add Buffer#dispose(), and smalloc is
its own cpp api anyways. So instead create a new require('smalloc') to
expose the previous Buffer.alloc/dispose methods, and expose copyOnto
and kMaxLength as well.

Other changes:
* Added documentation and additional tests.
* smalloc::CopyOnto has changed from using assert() to throwing errors
  on bad argument values because it is not exposed to the user.
* Minor style fixes.
tools: make check-imports.sh work on bsd-likes
src: add IsFunction() assert to MakeCallback

Helps catch bugs early on. Without it, V8 throws the fairly
unhelpful exception "TypeError: undefined is not a function" -
unhelpful because there is no stack trace.
src: fix persistent handle lifecycle issue

Commit 636ca7c adds an optimization that casts strong Persistent<T>
handles directly to Local<T> handles to avoid the overhead of creating
new HandleScope-rooted Local<T> handles all the time.

One gotcha that I missed is that it's no longer legal to reference the
Local<T> after calling Persistent<T>::Dispose(). This commit addresses
that.
buffer: return offset for end of last write
src: ReqWrap now optionally accepts a wrap object
udp_wrap, tcp_wrap: add out arg to AddressToJS

Prep work for removing process._errno. The handle.getsockname() function
will return a status code in the future and set the address and port
properties on the object that's passed in from JS land.
deps: upgrade libuv to 3ee4d3f
src: add libuv bindings module

Exports:

* all UV_E* error codes
* a uv_err_name() binding
src, lib: deduplicate errnoException
src, lib: update after internal api change

Libuv now returns errors directly.  Make everything in src/ and lib/
follow suit.

The changes to lib/ are not strictly necessary but they remove the need
for the abominations that are process._errno and node::SetErrno().
test: fix up tests after internal api change
bench: fix up benchmarks after internal api change
src: fix windows build error from 221c689e

Just forward declare struct sockaddr, the struct is never actually
dereferenced in src/node_internals.h.

Before this commit, it included sys/socket.h but that header doesn't
exist on Windows.