removed the broken fps display and added a field for EncodedBy

fixes #4710

This ensures that the variables will be available as soon as the aout
is externally visible, and that there value will persist across inputs.

This also saves a bunch of lookup at each new input.

Those variables are inherited and they have no callbacks.

(Lets assume that uintptr_t is big enough, i.e. 32-bits).

 - get the mode string directly from the callback (new) variable value,
 - reduce locking scope,
 - fix read overflow: do not apply peak protection in "max" mode.

split out some functions from Open()
move static functions
sout_stream_id_t -> define struct as empty and use the pointer to store sout_input_t

functional change:
do not force asfh mux if user specified another one but only warn him (like for upd/ts)

makes data smaller:
 no need to store pointers to each item of the array

char *x[] = { "a", "b", "c" };
memory looks like => "a" "b" "c" (&x) &a &b &c

char x[][2] = { "a", "b", "c" };
memory looks like => (&x) "a" "b" "c"

macosx: move VLCFSPanel from VLCControls to VLCMainWindow since its the only class which should know about it

Close #5167

Some X servers cannot borrow VLC user privileges to attach to its
shared memory segments. This fallback should fix MIT-SHM with those
X servers. However other users will be able to snoop on the decoded
video frames.

The SDL audio output is gone. The SDL video output is not very useful
and it won't quite work with most SDL video plugins disabled.

SDL is mainly a dependency for SDL_image.