Probably incorrect folly::crc32c usage

[MBkkt]

In general folly::crc32c have quite strange API, you need to mix it with ~0U manually.
For an example like here

Other implementations like abseil and rocksdb tries to avoid it:

1. rocksdb
2. abseil

Here it looks like a bug. Because folly doesn't have such xor, it will lead to same zero hash for any zero bytes input. Maybe it's not an issue if such input is impossible, but it's still quite complicated usage without xor with ~0U

Also here is two, symmetric, usage, they're probably correct, but it's not crc32c isn't it?

1. write
2. read