cutils: Fix size_to_str() on 32-bit platforms

cutils: Fix size_to_str() on 32-bit platforms

When extracting a human-readable size formatter, we changed 'uint64_t
div' pre-patch to 'unsigned long div' post-patch. Which breaks on
32-bit platforms, resulting in 'inf' instead of intended values larger
than 999GB.

Fixes: 22951aaa
CC: qemu-stable@nongnu.org
Reported-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 754da86714d550c3f995f11a2587395081362e0a)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>