Build/install lib/libc/tests/hash/t_sha2 if MK_OPENSSL == yes

Reported by: Beeblebrox <zaphod@berentweb.com>
Fix the function signatures when MK_CRYPT == no for snmp_get_local_keys and
snmp_passwd_to_keys

MFC after: 1 week
Reported by: Beeblebrox <zaphod@berentweb.com>