Remove the libvlc global lock

Remove the libvlc global lock

We have enough static locks in libvlc, I think: the
configuration R/W lock, the module bank mutex, the system-specific
initialization mutex, the message subscription R/W lock, the sets
of mutexes for initializations of specific libraries, the LibVLC
thread variable mutex, the configuration file mutex, the PRNG mutex,
the object pipe mutex, the object name mutex, the dialog provider
mutex, the interface module registration mutex, the OSD mutex, the
VLM mutex, the HTTP hosts mutex and the OSD mutex...