This patch extends the types on which the align parameter attribute is
permissible to include vectors of pointers. It does so in order to allow
alignment specification on llvm.vp.gather and llvm.vp.scatter
intrinsics, which lack an explicit alignment parameter.
The default alignment of these intrinsics was previously documented as
being equal to the ABI alignment of the *scalar* type, when in fact that
wasn't the case: the ABI alignment of the vector type was used instead.
This has also been fixed in this patch.