Commit gross hack and undef ifi_epoch.

This is not the right change, but it's nice to have things build on
FreeBSD -CURRENT.
Fix connscale build (fixes #17.)

Use uinet_soreadable instead of the shortlived uinet_sogetrxavail.

Adjust for new uinet_interface_up syntax.

Use UINET_SYNF_REJECT_RST instead of UINET_SYNF_REJECT.