Do not disturb buffer positions on OffheapStorageArea writes

[cschanck]

Currently, all the write methods in OffheapStorageArea disturb the buffer position of the underlying ByteBuffer. This has the unfortunate side effect of not allowing read operations to proceed while a write is happening, even if they are on non-colliding memory addresses, if those reads/writes happen to share an underyling buffer.

If this is fixed (simple application of slice() or duplicate()), then you could let can allow for reads to happen coincident with writes, assuming you know they are different spans. StampedLocks and optimistic reads, for example.