New **experimental** adaptation of XModem called XMX.COM:
- Fixes occasional "stall" at startup (I think)
- Reduces HBIOS overhead substantially
- Automatically uses the console port no matter what COM port the console is on
- Extended startup timeout for XM.COM so that it doesn't timeout so quickly while host is selecing a file to send.
- Updated SD Card How-To from David Reese.