control/media_descriptor.c: Send a libvlc_MediaDescriptorFreed event, when the md is freed. (Patch by Enrique Osuna).

* added a version check of the current Mac OS X version, as we require 10.4.x or higher and will definitelly crash on earlier releases.

Supposed to be useful.

Qt4 - time left implementation. Do it better, faster, with also a middle click, and fix the double click toggling time left bug.

dbus: don't lock the playlist, but only yield the input to prevent its destruction while we are accessing it.
We do that because we can't lock the playlist when we're in the input "state" callback because we MAY have been called by playlist_Control(), which does lock the playlist, and then call us.
ref #1346

screensaver: removes unused variable

Better solution would be to make sure interface threads lock their object ALL THE TIME, except when waiting on its condition variable, so we do never "loose" condition signals. However, I am not sure if this would not result in a deadlock, should the interface need to lock another object (typically, playlist, input and/or vout).  Also, we would need to have all thread call vlc_thread_ready(), otherwise, we could also miss the signal if it happens right after the thread is created => this requires fixing every interface, except those that don't have a pf_run.

dbus: monitors input "state" variable to emit the TrackChange signal only when the metadata has been read

- Enable building of libamrnb and libamrwb (disabled by default). To enable add HAVE_AMR to config.mak and make sure to rebuild ffmpeg too.
- Bumped up libdvbpsi version number to 0.1.6