Improved Windows (Cygwin/MSYS) support

Added new CYGWIN_PATH variable for usage with reset command under Cygwin
Changed RESET_CMD structure under Cygwin
Changed behaviour of get_monitor_port under Windows

Please note that you have to use the lowercase Windows 'com' style MONITOR_PORT variable, eg.
MONITOR_PORT = com3

Tested under Windows with MSYS as well as Cygwin