This function returns of list of hacks that are needed for codec
initialization, and also include IgnoreOmxDecoderPadding hack.

Remove OMX.MTK.VIDEO.DECODER.MPEG4 from blacklist since it only need a valid
CSD.

Rename it to pf_process_output. The output buffer is now dequeued/parsed
outside of the pf callback.

This commit also removes the decoder_NewPicture HACK to know if decoder is
flushing.

Split put_in into dequeue_in and queue_in.
Split get_out into dequeue_out and get_out

When the thread is cancelled, it will be exited before processing all input
blocks.

This does not make any sense. Spaces are normally encoded as %20 (+ is for
query parameters values only).

Also fix variable shadowing.