hybrid text/binary mount

[DJ Delorie]

> I was thinking that if a file had any characters whose ASCII code was
> < ' ' or >= DEL before the first \n, then the file would be considered
> binary.  Otherwise, the file would be text.  You could apply this heuristic
> to both input and output.

It's hard to apply it to output, because you don't know what the
program is going to write out.  At least on input, you can read a big
chunk (buffering does this anyway) and run some tests on the existing
data.

InfoZip has an automatic converter; we should see what heuristics it
uses, since it has a lot more history than we do.