Replaced LookupResult::IsProperty by LookupResult::IsFound where possible.

Replaced LookupResult::IsProperty by LookupResult::IsFound where possible.

Yak shaving for map sharing with accessor properties contd.: When CALLBACKS can
have map transitions, simply looking at the property type is not sufficient
anymore to decide if a property is there or not. One has to look at the actual
contents of the descriptor entry then, but this breaks down sometimes when the
lookup is being done with a NULL holder. Luckily enough, we can oftren replace
IsProperty by the simpler IsFound, because we inspect the type immediately
afterwards, anyway.

Committed: https://code.google.com/p/v8/source/detail?r=10474

[danno, 2012-01-23 11:08:28]

lgtm