The previous fix made the fetcher and preparser persistent throughout
the lifetime of the playlist. So we don't need to protect the pointers
anymore. Also, they are internally thread-safe (with their own lock).

They do not create threads anymore (unless they have work to do).

LibVLC needs this because we are sloppy programmers^W^W^W^Wit still
depends on the playlist for item meta infos (it should probably
instantiate the fetcher and preparser directly).

Also, do not create the preparser if there is no fetcher.

This makes the interface more comprehensible and allows for
input_item_node_Append[x] functions to be used for general node manipulation
without side effects, if needed in future.

 - remove pf_run no longer in use
 - attach object as soon as possible to benefit var heritage

for the video decoder on OMAP

It should fix it when input and output pictures don't have the same
properties (close #3063).

It will avoid selecting a non subtitle page at the core levels.

And replaced QVLCIconLabel with QVLCFramelessButton.

They are not supported.

They are not the same as the chroma plane are swapped.