Multiline input example

[jubalh]

Would you mind adding a multiline input example?

[ulfalizer]

I think this should work:

1. Do something like what this StackOverflow answer does to preserve newlines in the input (there seems to be some other good links too when googling "readline multiline").

2. Modify the strnwidth() code so that instead of just returning the width (x coordinate), it returns an x/y coordinate. When you see a newline in the input, do x = 0; y++;.

3. Use the returned x/y to position the cursor.

Might be quite a big change though, and I want to keep rlncurses.c relatively simple. If you come up with something that works, I'm happy to link it though. Could add it as a separate example in the repo too.

Might look at it myself some time. No guarantees though.