Issue 201. Never return NULL from kmem-alloc to rule out this simple case.
For Issue 201. Also check that mutex allocation was successful, or panic.
Add sysctl to monitor total mutex usage
Add MUTEX_LEAK conditional to maintain list of mutex allocations and
dump contents on SPL.kext unload.
Build a list with each mutex_init and remove with mutex_destroy, to
dump a list of mutex allocations that have not been destroyed on unload.
Bring back kstat counters for active mutex, and active rwlocks.
Enable mutex leak accounting again.
Start on kmem_fini unloading and cleanup.

Merge branch 'mutex_leak' into pk2

Conflicts:
	module/spl/spl-kmem.c
	module/spl/spl-mutex.c
	module/spl/spl-osx.c
Merge branch 'pk2' of github.com:openzfsonosx/spl into pk2

Conflicts:
	module/spl/spl-kmem.c