Add grnxx::map::BytesPool as a new version of grnxx::map::BytesStore.
Add tests for grnxx::map::BytesPool.
Add grnxx::map::BytesPool::get_page_size_in_use().
Update grnxx::map::BytesArray to use grnxx::map::BytesPool.
Update grnxx::map::DoubleArray to use grnxx::map::BytesPool.
Enable the 3rd argument of grnxx:map::BytesArray.
Remove grnxx::map::BytesStore.
Voidify sweep().