Fix Bytes when Vec pointer's LSB is set (#346)

This separates the `SharedVtable` into 3:

- `PromotableEvenVtable`: The original `SharedVtable`, which will
  promote the `Vec` to `Shared` on the first clone, and is selected when
  the `Vec`'s pointer has the LSB unset.
- `PromotableOddVtable`: Similar to the `PromotableEvenVtable`, but
  selected when the `Vec`'s pointer has the LSB set. This vtable differs
  in the masking used when reconstructing the `Vec`.
- `SharedVtable`: This no longer checks if its current kind is `VEC` or
  `ARC`, and is only created by the "promotable" vtables.

This also adds a test using an "odd" global allocator that purposefully
bumps all pointers with alignment of 1.

Closes #343

0 files changed, 0 insertions, 0 deletions