now reproduced also in UDP, not only ICMP
This patch also allows for a better ISO/OSI layer separation between
IPv6 and upper layers, and upper layers can use the same common
interface
actually only one packet is managed at a time,
then a packetin+packetout buffer area has been created for IPv6 packets.
Upper layers can then access this data by means of pointer,
avoiding further allocations on the stack.
Obviously, packetin is read-only (eg. upper layers can only read it)
when the escape char was read from serial, then the escaped char was
read immediately after, but it was not available, thus resulting in
no proper escape; now fixed
