log_crypt_101_read_checkpoint(), log_crypt_101_read_block():
Declare as ATTRIBUTE_COLD. These are only used when
checking that a MariaDB 10.1 encrypted redo log is clean.

log_block_calc_checksum_format_0(): Define in the only
compilation unit where it is needed. This is only used
when reading the checkpoint information from redo logs
before MariaDB 10.2.2.

crypt_info_t: Declare the byte arrays directly with alignas().

log_crypt(): Use memcpy_aligned instead of reinterpret_cast
on integers.