Improved Windows (Cygwin/MSYS) support

Changed RESET_CMD structure under Cygwin
Changed behaviour of get_monitor_port under Windows

DEVICE_PATH always becomes/dev/ttyS[0-9] on Windows
MONITOR_PORT always becomes com[0-9] on Windows
Merge pull request #297 from PeterMosmans/cygwincom

Improved Windows (Cygwin/MSYS) support