Make getTypeSizeInBits work correctly for array types; it should return

Make getTypeSizeInBits work correctly for array types; it should return
the number of value bits, not the number of bits of allocation for in-memory
storage.

Make getTypeStoreSize and getTypeAllocSize work consistently for arrays and
vectors.

Fix several places in CodeGen which compute offsets into in-memory vectors
to use TargetData information.

This fixes PR1784.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97064 91177308-0d34-0410-b5e6-96231b3b80d8