[Simh] Updated Ethernet executables based on gcc

[bsupnik at comcast.net]

I've replaced the Ethernet executables yet again, with executables compiled under Mingw.  

To do this yourself,

1) Download Winpcap 4.0 and the development kit from winpcap.org
2) Install Winpcap 4.0
3) Unzip the development kit
4) Copy the include directory to C:\Mingw\include
5) Copy libwpcap.a and libpacket.a to C:\Mingw\Lib
6) Build the source set with build_mingw_ether.cmd

/Bob Supnik