Adding pool memory management

[dcharkes]

We've landed samples with pools for memory management. We'll migrate this sample to this repo.

This will include changing the allocate and free, and the Utf8 and Utf16.

If you've any feedback on the sample before I merge this into the this package, please let us know.

[dcharkes]

The samples have been updated, and are not conflicting with package:ffi anymore.

We could opt to add a Pool extends Allocator here, but we don't have to. Users can also write their own pools.

Closing this issue. If there is a need for adding a Pool in this package, please reopen.