buffer: rename internal/buffer_new.js to buffer.js

The old smalloc-based implementation has been removed, the typed array
implementation is the only one that is left now.

PR-URL: https://github.com/nodejs/io.js/pull/2022
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

node.gyp

@@ -69,7 +69,6 @@
       'lib/vm.js',
       'lib/zlib.js',
       'lib/internal/child_process.js',
-      'lib/internal/buffer_new.js',
       'lib/internal/freelist.js',
       'lib/internal/socket_list.js',
       'lib/internal/repl.js',