Fix PreviousLine and NextLine on linux

[System-Glitch]

References:

#300 #302 #307 #308

I think this change will be enough to make it work on both Windows and Linux. I have tested in cmd.exe on windows, and on Ubuntu Konsole and VSCode integrated terminal. I cannot test on MacOS though because I don't own a Mac.

Logic behind this change:

In cursor_windows.go, PreviousLine() calls Down() and HorizontalAbsolute(), so I just did the same for linux but without HorizontalAbsolute() because it is apparently not needed (Test it on MacOS and tell me if it works. If it doesn't, then I think adding a call to HorizontalAbsolute() would do the trick). This allows us to keep PreviousLine() and NextLine() and don't have a conflict in naming between the windows and other versions.

[AlecAivazis]

Thanks for getting this out so quickly. I am a bit confused tho, your original PR made the switch from NextLine to Down - doesn't this change have the same effect as before?

[System-Glitch]

@AlecAivazis My previous PR replaced all occurrences of function calls for PreviousLine() and NextLine() with Up() and Down(). For Linux terminals, the result is the same. However, an unforeseen effect of that was that is broke the lib for windows because on windows you need HorizontalAbsolute(), which was not called anymore because of the replacement.

[AlecAivazis]

@System-Glitch - finally got my hands on a mac laptop. I will pull this down now and give it a shot

[System-Glitch]

@AlecAivazis I got a friend of mine test it for me on mac and everything appears to be working correctly.

[AlecAivazis]

I was also able to confirm that the behavior is consistent across mac and windows. Thanks for being patient 👍