Small cleanup which addresses a warning regaring the truncation
of a 64-bit entity to a 32-bit entity. This issue was reported by
Peter Kasting from Google.

MFC after: 3 days
Use a consistent type for the number of HMAC algorithms.
This fixes a bug which resulted in a warning on the userland
stack, when compiled on Windows.
Thanks to Peter Kasting from Google for reporting the issue and
provinding a potential fix.

MFC after: 3 days