exec/memop: Adding signed quad and octo defines

exec/memop: Adding signed quad and octo defines

Adding defines to handle signed 64-bit and unsigned 128-bit quantities in
memory accesses.

Signed-off-by: Frédéric Pétrot <frederic.petrot@univ-grenoble-alpes.fr>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20220106210108.138226-3-frederic.petrot@univ-grenoble-alpes.fr
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>