title: Display underscore rather than subscript in gnuplot titles
body: <p><strong>Short question</strong>:
  How do I display the <code>_</code> (underscore) character in a title in gnuplot that is assigned from a variable name in gnuplot?</p>
  
  <p><strong>Details</strong>:
  I have something like the following code:</p>
  
  <pre><code>items = "foo_abc foo_bcd bar_def"
  do for [item in items] {
    set title item
    set output item.eps
    plot item."-input.txt" using 1:2 title item with linespoints
  }
  </code></pre>
  
  <p>This works fine with gnuplot except that the title get changed from foo_abc to foo<sub>a</sub>bc.  I don't know if I want to use an escape character because I don't want that to be in the file name.  I've tried a couple of different options with single vs. double quotes but I haven't found what I need yet.</p>