Unified all three NIC families' DP8390 chip implementations in net_dp8390.c/h;
Some fixes for the WD8013EBT NIC;
Network status bar icon updating is now done at WinPcap/SLiRP handler level, not at the NIC level anymore.
Several bug fixes;
Preliminar addition of the SDL 2 renderer (does not yet work correctly in full screen mode);
SCSI devices no longer have configurable LUN's (this matches the configurability of real SCSI devices);
SCSI LUN's are now handed by the device's handler;
Removed all unused strings;
Removed some unused code files;
Significantly rewrote the bus mouse emulation.
