RegionStoreManager::getSizeInElements used 'int' for size
calculations, and ProgramState::assumeInBound fell back
to 'int' as well for its index calculations. This causes
truncation for sufficiently large sizes/indexes.
Initialize the ArrayIndexTy to ssize_t and use it in
these instances to prevent overflow problems.
One test was allocating an array greater than half
of the address space, which causes problems with
signed sizes. The array size was lowered.