automatic find tty(s)

Changes since 2.0.000

* rename to DeskLink2 / dl2
* support cygwin/msys2
* add co2ba.sh
* add PAKDOS
* add TSLOAD
* document (though not impliment) NADSBox extensions in constants.h
* more accurate pdd2 constants (commands, responses, & error codes) thanks to new service manual
* add pdd2 version & sysinfo commands
* pdd2 sector access, headers increased from 4-byte ID to 12-byte ID + 1-byte unknown
* add pdd1 fdc search ID command