Version 0.4.3 (the real one): fix Gentoo ip config failures and crashes

This version fixes problems with locating the 'ip' command on Gentoo
and possibly other Linux systems, and a problem that could cause a
crash if EthernetTap was unable to locate one of the commands it
invokes to configure IP information on tap devices.

The code also now builds on Windows. It doesn't run yet, but it's a
step. Windows port is in full swing.

Finally, the multicast rate limit defaults were raised a little. More
testing is needed here, and real world measurments.