udpburst: get rid of ipv4mapped sockets in favor of ipv4 and ipv6 socket

Since we can't get ipv4 events from an ipv6 mapped socket, switch
server to using individual sockets for each protocol. This of course
add some complexity, and requires poll (which is not completely done yet),
but we can now sweep ipv6 and ipv4 tos values correctly.

It is a shame and a PITA to have to keep protocol version related state
around. However ipv6mapping doesn't work by default on some arches anyway,
so this is sort of a win.

d@puck:~/git/isochronous$ ./udpburst -f -C -c 16 ::1
64 bytes -- received 16 of 16 -- 16 consecutive 0 ooo 0 dups 4 ect

1112131415161718191a1b1c1d1e1f
d@puck:~/git/isochronous$ ./udpburst -f -C -c 16 localhost
64 bytes -- received 16 of 16 -- 16 consecutive 0 ooo 0 dups 4 ect

2122232425262728292a2b2c2d2e2f