convert bcopy to memcpy. from david hill

for key material that is being being discarded, convert bzero() to
explicit_bzero() where required
ok markus mikeb

match libc sha2(3) API changes for kernel; ok millert@

Implementation of the HMAC-MD5, HMAC-SHA1, HMAC-SHA256, AES-128-CMAC
and AES Key Wrap algorithms.
They will replace/extend the non-generic implementation in net80211.

AES-128-CMAC tested by sobrado@ (AlphaServer 1200),
naddy@ (alpha/sparc64) and sthen@ (sparc64, armish).
HMAC-* reviewed by hshoexer@

ok and hints from djm@