Fix expectations for PointerAccessChains/pointer_index_is_constant_1.…

…cl (#1298)

The new code is correct.  The constant indexing into an array of arrays
of floats collapses into a constant index of an array of floats.

Ref #1292

Update LLVM (#1011)

Contributes to #1005

* Update PassBuilder constructor
* Fix test
* Disable rewrwite packed structs when opaque pointers are present