smalloc: prevent double free on dispose()

dispose() free's the memory when executed and sets the external array
data to NULL and length to zero.

To prevent the same memory from being free'd twice when the object is
garbage collected we first check if the object's external array data
length == 0. Since alloc() passes NULL to
SetIndexedPropertiesToExternalArrayData() if length == 0 there's no
opportunity for memory leak.
src: kill isolate on exit

Otherwise it's not possible to check from inside a destructor if V8 is
still alive with v8::V8::IsDead().  In V8 3.25, that function returns
true until the last isolate is destroyed.

This used to work in v0.10 and is a standard trick to dispose persistent
handles conditionally.

Signed-off-by: Fedor Indutny <fedor@indutny.com>
smalloc: rework double free bug fix

Rework the fix from commit 6810132 in a way that removes ~60 lines of
code.

The bug was introduced in commit e87ceb2 (mea culpa) and is at its core
a pointer aliasing bug where sometimes two independent pointers existed
that pointed to the same chunk of heap memory.

Signed-off-by: Trevor Norris <trev.norris@gmail.com>
benchmark: Add a test to measure Buffer.slice perf

Buffer.slice can be expensive. One regression was reported by https://github.com/joyent/node/issues/7633. The method should be benchmarked.
doc: Add a README for benchmark tests

The README.md documents how to run node core benchmark tests and
how to write new tests.
net: Ensure consistent binding to IPV6 if address is absent

See https://github.com/joyent/node/issues/7675
net.server.listen() behaves inconsistently depending on whether the port
number is provided.

1. port === 0 && host == '' (i.e. false-y), node creates an AF_INET
socket but does not call bind().

2. port > 0 && host == '', node creates an AF_INET6 socket and calls
bind().

The fix makes 1 consistent with 2.

Signed-off-by: Fedor Indutny <fedor@indutny.com>
fs: close file if fstat() fails in readFile()

Currently, if fstat() fails in readFile(), the callback
is invoked without closing the file. This commit closes
the file before calling back.

Closes #7697
src: replace CONTAINER_OF with type-safe function

Replace the CONTAINER_OF macro with a template function that is as
type-safe as a reinterpret_cast<> of an arbitrary pointer can be made.

Signed-off-by: Fedor Indutny <fedor@indutny.com>
build: initial cut of smaller-icu. Use a shell script to build normal ICU.
build: ignore deps/icu
doc: document --with-generic-icu option (experimental)
doc: actually preview the MD before committing.
build: reduce ICU code size a bit more
build: allow CORES to be an environment variable
build: further reduce ICU size, add documentation of special branch-in-progress
build: first cut at allowing v8 to build w/o brkiter (for space)
build: a little more trimming. English only clocks in at 19M.
build: initial cut of smaller-icu. Use a shell script to build normal ICU.
doc: actually preview the MD before committing.
build: reduce ICU code size a bit more