zshrc: Fixed `minimal-shell' function

zshrc: Fixed `minimal-shell' function

Well, it was actually completely broken. Because I fed an absolute path
name into `check_com()' without testing it - instead of using the
obvious test.

This also fixes an annoyance:

If infocmp returns an octal code such as this:
    backspace='\177'

That screwed up our special-string resolution, because mksh's `print'
builtin doesn't like \177 style octals. It *requires* them to look like
this: \0177 (leading zero).

We now just translate these strings like this:
    \\[1-7][0-7]*    =>   \\0[1-7][0-7]*

That should be fairly safe. - And this time, mika and me actually tested
the code before committing it. :-)