only define ARRAYSIZE_UNSAFE for NaCl builds

only define ARRAYSIZE_UNSAFE for NaCl builds

Now that C++11 is allowed, we can use arraysize instead of
ARRAYSIZE_UNSAFE, except in NaCl builds.  So let's move this
macro inside an NaCl ifdef.

BUG=chromium:405225
LOG=y
R=jochen@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=24875

[Mostyn Bramley-Moore, 2014-10-23 21:13:26]

mostynb@opera.com changed reviewers:
+ jochen@chromium.org

[Mostyn Bramley-Moore, 2014-10-23 21:14:14]

@jochen: PTAL.

[jochen (gone - plz use gerrit), 2014-10-23 21:16:28]

lgtm

[Sven Panne, 2014-10-24 13:21:24]

Committed patchset #1 (id:1) manually as 24875 (presubmit successful).

[Nico, 2014-10-25 23:02:15]

thakis@chromium.org changed reviewers:
+ thakis@chromium.org

[Nico, 2014-10-25 23:02:15]

Out of interest, what goes wrong if you don't explicitly check for nacl? I
believe we want all our toolchains to be c++11-capable, and the nacl irt build
switched to building with the pnacl toolchain to achieve this. Which
configuration did we miss?