Add an option to pass through input unmodified for WSL mode

[rprichard]

See #82 (comment).

[mintty]

Thanks a lot for handling this issue.
Passing --mouse to winpty would not be a problem in a preconfigured WSL package to solve mintty/mintty#558, but I wonder whether it would be needed because once escape sequences pass through, mouse sequences would be handled alike; we'll see.
[back in 10 days]

[rprichard]

The input escape sequences (e.g. mouse movements, button presses/releases) would go through fine, but the output sequences (e.g. enable/disable mouse mode) still wouldn't get through, so mintty would presumably handle mouse input by selecting text, rather than sending mouse escapes to the terminal program.

The --mouse option instructs winpty to output escape sequences to enable mouse mode. Ultimately, it forces winpty to output the escapes here.

Maybe --mouse could work for a preconfigured WSL package, but I think it'd require users to decide between mouse-mode and text-selection-mode before starting a WSL program.

[rprichard]

I think this approach won't be able to handle the DECCKM mode, where the arrow keys generate an \eO prefix rather than \e[. Because winpty is scraping the output buffer, it wouldn't propagate the \e[?1h string that switches the mode, so the terminal would continue to send normal input. So far, I know that this breaks Midnight Commander (#90).

[mintty]

This request is now satisfied by wslbridge (many thanks),
so I think this issue can be closed.