title: Invalid preprocessing directive for #elseifdef in Xcode
body: <p>Why:</p>
  
  <pre><code> #ifdef SOME_TARGET_FLAG     
        &lt;some code here&gt;
      #elseifdef SOME_ANOTHER_TARGET_FLAG
        &lt;some another code here&gt;
      #endif
  </code></pre>
  
  <p>produces <strong>"Invalid preprocessing directive" preprocess compilation error?</strong></p>
  
  <p>SOME_TARGET_FLAG and SOME_ANOTHER_TARGET_FLAG are just some "Other C-flags" defined in target build settings (<code>-D&lt;FLAG_NAME&gt;</code> pattern).</p>
  
  <p>Is <strong>#elseifdef</strong> directive not supported by Xcode?</p>