Fix Windows compilation for Crystal 1.13+

[HertzDevil]

Some of the internal definitions are no longer necessary and clash with a newer stdlib, especially crystal-lang/crystal#14501 which replaces C file descriptors with their underlying Win32 handles.

spec/reader_spec.cr will run on Windows too, however it lacks the proper fiber synchronization. Also it appears REPLy expects the input to use \r\n on Windows only, but the specs do not account for that.

What was the reason behind making Ctrl+Enter exclusive to Windows? Isn't it easier to just strip the CRLF sequences at the beginning of Reply::CharReader#parse_escape_sequence?

[I3oris]

Hello HertzDevil,

Thank you for this merge request!

In effect, spec/reader_spec is now running, but it needs to be fixed on Windows.

On Linux, the alt-enter shortcut allows users to input a new line without submitting the input. However, on Windows, this shortcut puts the terminal in fullscreen mode, and it seems impossible to change this behavior. That's why I implemented the shortcut on ctrl-enter on Windows. However, on Linux, ctrl-enter cannot be distinguished from enter because they share the same key code. Ditto for shift-enter.

[HertzDevil]

Alt+Enter can be disabled in Windows Terminal, not sure about the older console host