OS X compiler warning

[2016/01/21 20:48:54.033] src/third_party/wiredtiger/src/btree/bt_rebalance.c:146:7: error: format specifies type 'unsigned long long' but the argument has type 'size_t' (aka 'unsigned long') [-Werror,-Wformat]

 [2016/01/21 20:48:54.033]                     rs->leaf_next, UINT32_MAX);

 [2016/01/21 20:48:54.033] ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

 [2016/01/21 20:48:54.033] src/third_party/wiredtiger/src/include/error.h:51:27: note: expanded from macro 'WT_RET_MSG'

 [2016/01/21 20:48:54.033]         __wt_err(session, __ret, __VA_ARGS__);                          \