title: Adding the combining overline unicode character
body: <p>I'm writing a program that converts an integer to a Roman numeral.</p>
  
  <p>Roman numerals over 3999 are overlined, so IV overlined is 4000, CM overlined is 900'000, etc. These lines can stack.</p>
  
  <p>So as to not limit my program, stopping it at just 3999 isn't good enough.</p>
  
  <p>The question is, how do I add the "combining overline" unicode character to my string to achieve this?</p>
  
  <p>My program is written in Rust, but I suspect the solution is similar across most languages that support unicode strings.</p>