[orbis-kernel] Implement shared_cv

Shared (IPC-ready) condition variable.
Relicensed and improved from RPCS3.

orbis-kernel/include/orbis/utils/SharedMutex.hpp

@@ -101,6 +101,9 @@ public:
 
   // Check whether can immediately obtain a shared (reader) lock
   bool is_lockable() const { return m_value.load() < c_one - 1; }
+
+  // For CV
+  unsigned lock_forced();
 };
 
 // Simplified shared (reader) lock implementation.