Reusing settings from before 1.1.0 results in a mess.

This avoids "*-caching variable does not exist" errors

Now, we get the URL directly. This is much simpler and much less
confusing. Also a few missing network protocols.

Improves seeking experience by sending less seek requests and actually allowing output to update between them.

This follows the historical LibVLC semantic (and new --rate one), so
bigger is faster. In the process, simplify a few code paths, especially
those in LibVLC, but make many other code paths more complicated due to
integer<->float conversion. Most of those paths could probably be
simplified.

 * Fix RC "fastforward" command behaviour (it was slowing down instead)
 * Fix str_format_mera 'R' format string with negative rates and
   rates such that (rate % 1000 < 100).

This breaks our current Xlib XVideo and plain X11 outputs.
Qt4 would create an ARGB window for our embedded video. Then, the
Xlib plugins would raise BadMatch errors and VLC aborts. Starting
cairo-dock is an easy way to trigger this problem.
(With XCB plugins, we fail safe to OpenGL/GLX instead of crashing.)

We should instead handle ARGB visuals properly. But that would involve
more efforts, and would only enable plain X11, not XVideo anyway.

This should work around LP#416294.

This is ugly and not thread-safe. If you have a better idea, go ahead.
(cherry picked from commit c0ec5be56e71c273eef4faea8d927eeb3cbc7ec5)

Signed-off-by: Ilkka Ollakka <ileoo@iki.fi>

 * deleting non-existent callback is not allowed (-> abort),
 * adding a callback but not deleting it is a bad idea,
 * deleting a callback while setting the valeu can race against other
   interfaces.

--v4l-vdev is obsolete.

Seemed to work just fine, and didn't find any reason to keep that form.

Fixes #2899, at least on Linux. Can somebody test on Windows, please?

There was opportunity for playlist items not showing up in Qt playlist due to race between playlist rebuilding and item-added, item-removed callbacks
Maybe also fixes some aspects of #2297 or completely - to test.

Unparented dialogs are not supported by the window manager. This was
causing a deadlock during VLC startup (There may be other cases left).

QSystremTray class does not exist at all.