title: XCode 4.5 'tr1/type_traits' file not found
body: <p>I use the wxwidget library and I have the following problem:</p>
  
  <pre><code>#if defined(HAVE_TYPE_TRAITS)
      #include &lt;type_traits&gt;
  #elif defined(HAVE_TR1_TYPE_TRAITS)
      #ifdef __VISUALC__
          #include &lt;type_traits&gt;
      #else
          #include &lt;tr1/type_traits&gt;
      #endif
  #endif
  </code></pre>
  
  <p>here the  #include  isn't found. I use the Apple LLVM compiler 4.1. (with the c++11 dialect).
  If I switch to the LLVM GCC 4.2 compiler I have no error there, but the main problem is that all the c++11 inclusions won't work.</p>
  
  <p>How can I either use the GCC compiler, but with the c++11 standard or make it that the LLVM can find the ?</p>
  
  <p>any help would be really appreciated.</p>