Fix vstore/vload/setelementat.

This contains two fixes. The first removes the readonly attribute
from vstore functions.

The second fixes 64-bit operations with vectors greater than 128
bits.

ll64/allocation.ll was based on ll32/allocation.ll, but the
AArch64 calling convention passes vectors greater than 128 bits
on the stack rather by value.

This fixes vload/vstore/SetElementAt.

bug 17615222

Change-Id: Ib8e2633f9b1236c8b360929b9ca5fe53ebb24703
3 files changed