title: error: 'mutex' in namespace 'std' does not name a type in gcc 4.6.2
body: <p>Simple program like this</p>
  
  <pre><code>#include &lt;iostream&gt;       // std::cout
  #include &lt;thread&gt;         // std::thread
  #include &lt;mutex&gt;          // std::mutex
  
  std::mutex mtx;           // mutex for critical section
  
  int main ()
  {
       return 0;
  }
  </code></pre>
  
  <p>Tried the following to compile </p>
  
  <pre><code>$ /usr/local/Cellar/gcc46/4.6.4/bin/g++-4.6 -std=gnu++0x -I/usr/local/Cellar/gcc46/4.6.4/gcc/include/c++ -L/usr/local/Cellar/gcc46/4.6.4/gcc/lib temp_mutex.cpp 
  temp_mutex.cpp:6:1: error: 'mutex' in namespace 'std' does not name a type
  </code></pre>
  
  <p>By the way I am compiling on Mac.</p>