This patch introduces struct pp_globals in include/ppsi/pp-instance.h
and starts using it in arch-gnu-linux. Actually, the behaviour does not
change yet, and only one interface is taken into account. In main-loop.c
there is a proposal for interfaces enumeration, based on runtime env
variables:
- one PPROTO_IF_NUM (number of interfaces);
- many PPROTO_IF_XX (each one defining an interface name).
Signed-off-by: Aurelio Colosimo <aurelio@aureliocolosimo.it>