Add up to 256 bytes of padding for compressed+encrypted files.
This will obscure the obvious cases of extremely compressible content
and leave a similar output size for a very wide variety of inputs.
This does *not* mean the compression ratio doesn't leak information
about the content, but the outcome space is much smaller,
so often *less* information is leaked.
This is to ensure that there are no projects
that try to import `minio/minio/pkg` into
their own repo. Any such common packages should
go to `https://github.com/minio/pkg`
