Locks the layer. Returns when the layer is locked for exclusive use. This call behaves like when a semaphore is locked. The same task may lock the same layer several times without locking itself out. For every call to this function a call to UnlockLayerRom() has to be made as the calls nest. This function will also prevent intuition from locking the layer so the layer should not be blocked too long. This function does exactly the same as layers/LockLayer()