Revert some errors in 85943656 and 9630c00c

assert that pf_control is available

0x11 is the type for AAC synchronized with LOAS
0x0f is the type for AAC synchronized with ADTS

Not everybody builds VLC from the source tree
besides that the shell code was wrong : the return value of a pipe is the one of the LAST command in the pipe.

This was triggered by DBus module using access2_Control

Refactor video_filters in modules/stream_out/transcode.c by abstracting common code into 2 new functiosn transcode_video_filter_new() and transcode_video_filter_close().