Make tests pass on MoarVM Linux x86_64

- use explicit integer size with CArray
- update Buf creation syntax in basic.t
Fix calling functions on bufs/blobs
Add more digest functions

This appears to be all the ones that my OpenSSL knows about:
- md2
- sha0
- sha2 (224, 384, and 512 bit variants)
- whirlpool
Fix typo in README
Merge pull request #1 from avuserow/master

Fix on current MoarVM/64-bit Linux, add more hash functions, and allow hashing of Bufs/Blobs