Add some bits to the PPPoE section:
o PPPoE & Netgraph are available from 3.4 onwards
o Mention that NETGRAPH_SOCKET and NETGRAPH_PPPOE are optional
o Remove the ``set login'' bit
o Xref the PPPoEwithNAT tag in the FAQ
o DON'T suggest that -dedicated mode is used. PPPoE is probably

the worst place in the world to use the -dedicated flag (which allows
LCP to come down, but doesn't close/reopen the link before starting
LCP again!)