Express LoadIC extra ic state with LoadIC::State

Express LoadIC extra ic state with LoadIC::State

Soon we will create code stubs that need to match LoadIC state. It's easier to
express if the state is encapsulated in a single class rather than multiple bit
fields.

Also, eliminate ContextualMode as it's a synonym for TypeofState.

R=verwaest@chromium.org
BUG=

[mvstanton, 2014-07-22 16:13:20]

Hi Toon,
Here is the CL we discussed, thanks for the look!
--Michael

[Toon Verwaest, 2014-07-23 11:06:46]

As discussed offline, please mark all loads properly as not inside typeof when
they are not. That'll require you to check IsGlobalObject() whenever you want to
check the typeof flag. Perhaps do something like:

function IsContextLoad(o) { return IsGlobalObject(o); }
function IsReferenceError(it) {
  return !it->IsFound() &&
         IsContextLoad(it->GetReceiver()) &&
         !target()->inside_typeof();
}