title: Find-replace-regexp with elisp replacement not working correctly
body: <p>I have a string in a buffer <code>"THIS_IS_A_TEST"</code> (the quotes are part of the string).</p>
  
  <p>I want to turn this in to <code>"ThisIsATest"</code>. I'm attempting to do this using a <code>query-replace-regexp</code> where I substitute <code>\(\w+\)_?</code> with <code>\,(capitalize \1)</code>. However, the upcased words are not being capitalized.</p>
  
  <p>Running <code>M-c</code> (<code>capitalize-word</code>) on any of those words works fine, and if my test string is changed to  <code>"this_is_a_test"</code>, then I get the desired result (<code>"ThisIsATest"</code>). </p>
  
  <p>What's going wrong? Is this a bug in capitalize?</p>
  
  <p>(Note that this still happens without an init file loaded)</p>