fixed wscript to link custom dprintf only for debug

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
gmedec: only declare debug printf if CUSTOM_DPRINTF_FUNCTION is present

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
baseclass: make sure negotiation happens before the segment is defined

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
baseclass: beginning modifications for supporting decoders like uade or M1

uade and M1 read files directly; they expect filenames, and it is not
possible to give them a memory block. Therefore, with these decoders,
the element cannot have a sinkpad.

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>