Bug 850080 - Make root analysis check Rooted<Value> as a non-pointer type; r=sfink

In 32bit builds, Value does not have the same size as void*; thus, we cannot do
a simple address comparison in this case.

--HG--
extra : rebase_source : 1dfb86965c1aa873c26660b67d9add0d5d0a91d7