BUG/MEDIUM: random: align the state on 2*64 bits for ARM64

BUG/MEDIUM: random: align the state on 2*64 bits for ARM64

x86_64 and ARM64 do support the double-word atomic CAS. However on
ARM it must be done only on aligned data. The random generator makes
use of such double-word atomic CAS when available but didn't enforce
alignment, which causes ARM64 to crash early in the startup since
commit 52bf839 ("BUG/MEDIUM: random: implement a thread-safe and
process-safe PRNG").

This commit just unconditionally aligns the arrays. It must be
backported to all branches where the commit above is backported
(likely till 2.0).