Fix overflow in arm simulator.

Fix overflow in arm simulator.

Don't copy 64 bits to a 32 bit value.

R=karlklose@chromium.org,sgjesse@chromium.org
BUG=
TEST=

Committed: http://code.google.com/p/v8/source/detail?r=7788

[Karl Klose, 2011-05-05 05:52:45]

LGTM.

[Søren Thygesen Gjesse, 2011-05-05 06:23:42]

LGTM