A new CRCHasher class wraps crc functions to mimic the hashlib
hasher interface.
For crc32, use the zlib implementation.
For crc32c, use ISA-L if we can find it; on py38+ this includes the
ISA-L bundled in pyeclib's binary wheels.
If ISA-L is not available, check for kernel crypto API support for crc32c;
use it if available. Otherwise, raise a NotImplementedError.
No callers yet, but these will be used by s3api in a later patch.
Change-Id: Ic0c55e307ce10b56b569c9fee728c445a2300cbd
b65855d715