I'd like to clarify the semantics of grow and unsafeGrow, and hopefully update the documentation appropriately. From looking at the code for boxed, unboxed, and storable vectors, it seems that in all cases, grow/unsafeGrow will create a new mutable vector and leave the original mutable vector unchanged. The upshot would be that it would be valid to modify the original vector without affecting the new vector, and vice-versa. Two questions:

1. Have I misread the code, and in fact that's not the way the current three vector types work?
2. Do we want to codify this contract in the documentation as a promise for future behavior?