libroot. The mutex is a simple benaphore, the rw_lock is pretty much the same
as the one from libkernelland_emu but uses a mutex per lock instead of emulating
a global thread lock. Also added MutexLocking and RWLock{Read|Write}Locking and
AutoLockers based on them. It's cased with __cplusplus so the locks are also
usable from C. Everything's currently exposed in shared/private/locks.h but I
think we should make these locking primitves public.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@33543 a95241bf-73f2-0310-859d-f6bbb57e9c96
