configure: disable -Wcast-align for arm architecture

The -Wcast-align flag causes a lot of compile warnings on ARM, which
are false alarms.

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
object_cache: fix dirty bitmap size

The type of bitmap for object cache is not unsigned long, but uint64_t.

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
collie: don't use uint64_t for atomic operations

Atomic operations against 64 bit integers are not allowed on 32 bit
architectures.  Using unsigned long instead of uint64_t fixes the
problem and doesn't hurt x86_64.

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>