Few fixes for 2020 :)

[sledzik1984]

[tomash]

I've tested @sledzik1984 's fork, it compiles and runs successfully on my Ubuntu 18.04 machine.

[CB750-Rider]

I ran into the same issue using gcc 9.3.0 on Ubuntu 20.04.2 LTS. As mentioned here: https://stackoverflow.com/a/51536663 the warning is doing what it is supposed to do. Since only one line was creating this warning it is better practice to fix that one line than to turn off the warning in the Makefile. As suggested, this can be done in interactive.c:140

snprintf(strFl,6,"F%03d",(a->altitude/100)) < 0 ? abort() : (void)0;