title: vimrc not accepting mouse-=a command
body: <p>I have strange problem with my <code>/etc/vim/vimrc</code> file.</p>
  
  <p>I was trying to get rid of VISUAL mode in VIM, so I have tried to add the <code>set mouse-=a</code> command in my <code>vimrc</code> file.</p>
  
  <p>However my vim does not take those changes into account.</p>
  
  <p>When I do <code>:set mouse-=a</code> in openend vim, it does what I want (selecting text with mouse without entering VISUAL mode), but the command does not work in the <code>vimrc</code> file.</p>
  
  <p>I have also enabled the "jump to the last position when reopening a file" in <code>vimrc</code> and it is working, that makes me even more confused.
  I have been trying every possible command:</p>
  
  <ul>
  <li><code>set mouse=a</code></li>
  <li><code>set mouse=r</code></li>
  <li><code>set mouse-=a</code></li>
  <li><code>:set mouse-=a</code></li>
  </ul>
  
  <p>None of them is working when added to <code>/etc/vim/vimrc</code>.</p>
  
  <p>My system is:</p>
  
  <pre><code>rRr-kali:~# uname -a
  Linux rRr-kali 4.8.0-kali2-amd64 #1 SMP Debian 4.8.15-1kali1 (2016-12-23) x86_64 GNU/Linux
  rRr-kali:~#
  </code></pre>