title: Default Omnicomplete support
body: <p>I just enabled omnicomplete function(I'm using Vim7.3) and I want to try it out so I wrote a test.c:</p>
  
  <pre><code>int main
  {
     int appleInc;
     app_
  }
  </code></pre>
  
  <p>"_"is where the current cursor is.But when I hit Ctrl X or Ctrl O, nothing pops up. It just say pattern not found.</p>
  
  <p>I'm a bit confused by this. Doesn't it at least supposed to support the variable autocompletion? 
  This is what I add in the .vimrc:</p>
  
  <pre><code>filetype plugin on
  ofu=syntaxcomplete#Complete
  </code></pre>