Fix undefined bit shift in sroa. (#2532)

There was a bit shift done on 32-bit values, but they should have been
done on 64-bit values.  This is fixed.  At the same time, uses of size_t
are repalaced by uint64_t to ensure these values are 64-bit.

A test case cannot be created because the code that was change is not
run at the moment since we do not split up vectors or matricies.  I do
not want to delete the code because I like to experitment with it every
once in a while.

Fixes #2528.