This changes crypt's use of sync.Pool: Instead of storing slices
it now stores pointers pointers fixed sized arrays.
This issue was reported by staticcheck:
SA6002 - Storing non-pointer values in sync.Pool allocates memory
A sync.Pool is used to avoid unnecessary allocations and reduce
the amount of work the garbage collector has to do.
When passing a value that is not a pointer to a function that accepts
an interface, the value needs to be placed on the heap, which means
an additional allocation. Slices are a common thing to put in sync.Pools,
and they're structs with 3 fields (length, capacity, and a pointer to
an array). In order to avoid the extra allocation, one should store
a pointer to the slice instead.
See: https://staticcheck.io/docs/checks#SA6002
9172c9b3dd