title: How to config VIM to support multiple asm syntax
body: <p>I have mainly two types of assembly files types:</p>
  
  <ol>
  <li>GNU AS</li>
  <li>ARM ASM</li>
  </ol>
  
  <p>And the filenames look like: <code>example.s</code> and <code>example.asm</code></p>
  
  <p>I download both syntax plugins for these two file types, and I add them into:</p>
  
  <pre><code>$HOME/.vim/bundle/vim-gas/
  $HOME/.vim/bundle/vim-armasm/
  </code></pre>
  
  <p>I set:</p>
  
  <pre><code>let asmsyntax='armasm'
  let filetype_inc='armasm'
  </code></pre>
  
  <p>then I can see the highlight for ARM asm file.</p>
  
  <p>I changed them to:</p>
  
  <pre><code>let asmsyntax='gas'
  let filetype_inc='gas'
  </code></pre>
  
  <p>Then I can see the highlight for GNU AS file.</p>
  
  <p>My question is how can I add both of them into one <code>.vimrc</code> file? I tried <code>+=</code> and it doesn't work.</p>