Disable cfi-unrelated-cast sanitizer in OpParameter function.

Disable cfi-unrelated-cast sanitizer in OpParameter function.

This function deliberately casts to an unrelated type. This is forbidden under
the cfi-unrelated-cast policy, but it is unclear how to fix the underlying
problem. This change at least unblocks things.

BUG=v8:3809
R=svenpanne@chromium.org,mstarzinger@chromium.org

[Sven Panne, 2015-06-19 09:05:26]

svenpanne@chromium.org changed reviewers:
+ bmeurer@chromium.org

[Sven Panne, 2015-06-19 09:06:22]

Hmmm, I'm not sure if this is the right way to proceed: With this CL, we
effectively just shut up the compiler without fixing the underlying
adventurous/creative use of C++'s dark corners. IIRC, OpParameter and/or the
related classes should change or vanish, but I can't remember the details. If
this is really the case, I think this CL should not be landed. Michi? Benedikt?

[Benedikt Meurer, 2015-06-19 11:28:13]

I think we should fix the bugs instead of trying to silence some warnings. I've
uploaded a fix for the issue, see https://codereview.chromium.org/1196623002