Fix bug 1070: set correct holder for primitive checks.

Fix bug 1070: set correct holder for primitive checks.

Code generated for checks starting with primitive receivers skips one step
in the usual prototype checking algorithm, so the holder must always be set.

Not setting the holder did not cause an immediate failure because our
primitives have additional hidden prototypes before the real prototypes.
These extra objects in the chain usually contain no properties and so
allowed the right holders to be selected.

Committed: http://code.google.com/p/v8/source/detail?r=6459

[fschneider, 2011-01-25 12:06:57]

LGTM.