title: Check if character is letter in Delphi (Unicode)
body: <p>Are there pre-defined charsets in Delphi, to check if a character is a letter?</p>
  
  <p>In Cocoa I use something like  </p>
  
  <pre><code>if ([[NSCharacterSet whitespaceCharacterSet] characterIsMember:character])
  </code></pre>
  
  <p>I know I can do in Delphi</p>
  
  <pre><code>if c in ['A'..'Z'] then
  </code></pre>
  
  <p>but will this cover foreign accentuated characters like Á, À, Ú, É, ....?</p>
  
  <p>What would be the most efficient way to check this in Delphi. I need to check if a string is fully composed with letters.</p>