Converts an ASCII string to ScanCode (IBM-style 101-, 102-, and 104-key keyboards).
Outputs ScanCode for KeyDown and KeyUp.
Useful for pre 5.2 VirtualBox command 'controlvm' with 'keyboardputscancode'. See https://www.virtualbox.org/manual/ch08.html#vboxmanage-controlvm
Note: Since VirtualBox 5.2 the subcommand 'keyboardputstring' is supported and works better than this implementation!