Overall construction time of Typed Arrays is faster in JS, but the
problem with using it normally is zero-fill of memory. Get around this
by using a flag in the ArrayBuffer::Allocator to trigger when memory
should or shouldn't be zero-filled.

Remove Buffer::Create() as it is no longer called.

The creation of the Uint8Array() was done at each callsite because at
the time of this patch there was a performance penalty for centralizing
the call in a single function.

PR-URL: #2866
Reviewed-By: Fedor Indutny <fedor@indutny.com>

Notable changes:

* buffer:
  - Buffers are now created in JavaScript, rather than C++. This increases the speed of buffer creation (Trevor Norris) nodejs#2866.
  - `Buffer#slice()` now uses `Uint8Array#subarray()` internally, increasing `slice()` performance (Karl Skomski) nodejs#2777.
* fs:
  - `fs.utimes()` now properly converts numeric strings, `NaN`, and `Infinity` (Yazhong Liu) nodejs#2387.
  - `fs.WriteStream` now implements `_writev`, allowing for super-fast bulk writes (Ron Korving) nodejs#2167.
* http: Fixed an issue with certain `write()` sizes causing errors when using `http.request()` (Fedor Indutny) nodejs#2824.
* npm: Upgrade to version 2.14.3, see https://github.com/npm/npm/releases/tag/v2.14.3 for more details (Kat Marchán) nodejs#2822.
* src: V8 cpu profiling no longer erroneously shows idle time (Oleksandr Chekhovskyi) nodejs#2324.
* v8: Lateral upgrade to 4.5.103.33 from 4.5.103.30, contains minor fixes (Ali Ijaz Sheikh) nodejs#2870.
  - This fixes a previously known bug where some computed object shorthand properties did not work correctly (nodejs#2507).

Refs: nodejs#2844
PR-URL: nodejs#2889

Notable changes:

* buffer:
  - Buffers are now created in JavaScript, rather than C++. This increases the speed of buffer creation (Trevor Norris) #2866.
  - `Buffer#slice()` now uses `Uint8Array#subarray()` internally, increasing `slice()` performance (Karl Skomski) #2777.
* fs:
  - `fs.utimes()` now properly converts numeric strings, `NaN`, and `Infinity` (Yazhong Liu) #2387.
  - `fs.WriteStream` now implements `_writev`, allowing for super-fast bulk writes (Ron Korving) #2167.
* http: Fixed an issue with certain `write()` sizes causing errors when using `http.request()` (Fedor Indutny) #2824.
* npm: Upgrade to version 2.14.3, see https://github.com/npm/npm/releases/tag/v2.14.3 for more details (Kat Marchán) #2822.
* src: V8 cpu profiling no longer erroneously shows idle time (Oleksandr Chekhovskyi) #2324.
* v8: Lateral upgrade to 4.5.103.33 from 4.5.103.30, contains minor fixes (Ali Ijaz Sheikh) #2870.
  - This fixes a previously known bug where some computed object shorthand properties did not work correctly (#2507).

Refs: #2844
PR-URL: #2889