title: Characters are not bold if there is a Greek character or enhanced text
body: <p>If a terminal font is set to bold and there are Greek characters in axis title, legend or label, or there are subscripts and superscripts, then the non-Greek characters are displayed with regular density. Is it a bug, or there is a way to display these characters bold? Gnuplot version is 4.6.7.</p>
  
  <pre><code>set term pngcairo enhanced font 'Arial Bold,20'
  set output 'test.png'
  set xlabel '{/Symbol g}123abc'
  set ylabel '123_4abc'
  set label '{/Symbol b}abc' at graph 0.5, graph 0.7
  set label 'abc' at graph 0.5, graph 0.4
  plot 1 t '{/Symbol g}123', 2 t '123456789'
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/FRjIy.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FRjIy.png" alt="enter image description here"></a></p>