[cairo] Please review my patch for Bug 90318: data races with freed_pool_t's |top| data member

[Wan-Teh Chang]

Hi,

I submitted a patch for Bug 90318: data races with freed_pool_t's
|top| data member. The patch adds atomic int load and store functions,
with the relaxed memory order, to cairo-atomic-private.h and
cairo-atomic.c, and uses the new functions in
cairo-freed-pool-private.h and cairo-freed-pool.c.

I would very much appreciate your review:
https://bugs.freedesktop.org/show_bug.cgi?id=90318#c5

Thanks,
Wan-Teh Chang