mot fifo file instead file

[YoannQueret]

mot pad file is currently a file created before mot-encoder start. Need to create a FIFO file with mkfifo instead.

[mpbraendli]

dabplus-enc will create the pad fifo (dabplus-enc.cpp +538) if it doesn't exist yet. mot-encoder fails if the fifo doesn't exist.

Maybe this can allow you to skip manual creation of the fifo.

[YoannQueret]

issue solved in next branch