macosx: fixed volume slider appearance in black intf mode and disable the track slider when appropriate

Audio output plugins can use this to expedite discarding pending
buffers. This reduces latency upon seeking or stopping the input.

This new callback also supports explicit draining, but this is not
used for the time being.

The date parameter is always zero, remove it.

Previously, most of the audio samples in the left in the output buffer
during pause where dropped out on resume. This should fix it.

See CVE-2011-2690 (we shouldn't be affected), CVE-2011-2691 (same),
CVE-2011-2692 (no idea)

- cosmetics ( xx ) -> (xx) (look at patch with -w)
- remove useless header inclusion
- move some variables from p_sys to Run() function scope
- fix invalid asprintf() return value checks
...

The metadata structure would not be zeroed when title or artist were missing

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

macosx: fixed cocoa error complaining about missing window server connection and reduced number of ticks for the speed control

It gave -static -no-install flags to vlc instead of vlc-static

This occurs when the output is really late (typically as a side effect
of glitches in pause/resume). Both FIFOs  are now both protected with
the same lock, so there is no room for race conditon between the two
identical checks anymore. So we can handle both checks in one go.