extern type errors in kstat_osx.h

[rottegift]

An example:

$ sysctl -h kstat.zfs.darwin.tunable.zfs_trim_extent_bytes_max
kstat.zfs.darwin.tunable.zfs_trim_extent_bytes_max: 140,737,622,573,056

which is way different from its definition in module/zfs/vdev_trim.c:

unsigned int zfs_trim_extent_bytes_max = 128 * 1024 * 1024;

and the problem is because in include/os/macos/zfs/sys/kstat_osx.h:

extern uint64_t  zfs_trim_extent_bytes_max;

Todo: check the types of all the externs in kstat_osx.h, and/or figure out how to generate some build-time warning about this to catch when this happens.