FEC: Change the default slice size from 1490 to 1472.

FEC: Change the default slice size from 1490 to 1472.

1472 is the maximal possible size that does not result in fragmentation
on networks with 1500 MTU size (1500 = 1472 payload + 8 UDP header +
20 IP header).

This can be verified using

	tcpdump -nv -i eth0 udp

The output must contain a zero offset value, and the "Don't Fragment"
IP flag (DF) should be set.

Thanks to Gerrit Renker for pointing this out.