Remove unused functions.

[lucc]

line_n() was not used since b8e8d98 and it
was the only place where tail was used.

If need be line_n() can also be reimplemented without tail with the help of
sed:

line_n() {
    line=$1
    shift
    sed -n "$line{p;q;}" "$@"
}

[rkitover]

I wouldn't remove tail just yet, it's used in vimcat for output streaming and may be needed in the future for other things as well. Also we can discuss this in the other PR.

[lucc]

This PR only removes the tail functions and related code from vimpager. This code was never even used in vimcat. vimcat used the tail executable in $PATH all along and only requires the -f option which was also never checked in the bootstrapping code.

And this is not only about tail but also about line_n.

[rkitover]

Right, I mean once we finish the platform stuff I will use it to find the best version of tail in vimcat as well.

I'm perfectly happy to see line_n removed, but I don't want to remove tail until it is somewhere else.

[rkitover]

@lucc ok I'm merging this, I saved a copy of the corrected tail code to prototypes/tail.sh in case it is ever needed.

Also I'm probably going to rewrite the output streaming code in vimcat to not use tail but a pipeline instead, so it won't be used there either.

[lucc]

The code is also i the git history :)

[rkitover]

@lucc I know, but I like to keep my experiments there, I'm going to factor them out into separate project(s) at some point.

Like for example I wanted to contribute my do_uudecode function to shar.