buffer: reapply 07c0667
buffer: reapply 07c0667

Original commit message:

    buffer: align chunks on 8-byte boundary

    When slicing global pool - ensure that the underlying buffer's data
    ptr is 8-byte alignment to do not ruin expectations of 3rd party C++
    addons.

    NOTE: 0.10 node.js always returned aligned pointers and io.js should
    do this too for compatibility.

PR-URL: https://github.com/nodejs/node/pull/2487
Reviewed-By: Trevor Norris <9cb5491eb5770dd8e0bf77a8a0335abf5f0488c5@gmail.com>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node