Make memory locking optional (mlock, VirtualLock).

Fix desired locking operation (to fix "sudo" memory).
It was discovered that some systems have outdated configuration.
With too tight limit, it's almost impossible to lock anything in memory.

rpcs3/util/vm.hpp

@@ -40,7 +40,7 @@ namespace utils
 	void memory_protect(void* pointer, std::size_t size, protection prot);
 
 	// Lock pages in memory
-	void memory_lock(void* pointer, std::size_t size);
+	bool memory_lock(void* pointer, std::size_t size);
 
 	// Shared memory handle
 	class shm