title: shared_timed_mutex not available on OS X 10.11.2?
body: <p>I'm trying to play around with the new <code>shared_timed_mutex</code> structures from C++ 14 on OS X 10.11.2 using Eclipse CDT 4.5.0. Xcode is 7.2. I'm using GCC C++ with the following options: </p>
  
  <pre><code>-O0 -g3 -Wall -c -fmessage-length=0 -std=c++14
  </code></pre>
  
  <p>Her's what I get:</p>
  
  <pre><code>Invoking: MacOS X C++ Linker
  g++  -o "MyProject" ./src/main.o  
  Undefined symbols for architecture x86_64:
    "std::__1::shared_timed_mutex::shared_timed_mutex()", referenced from:
    HashMap&lt;int, std::__1::basic_string&lt;char, std::__1::char_traits&lt;char&gt;,         std::__1::allocator&lt;char&gt; &gt;, std::__1::hash&lt;int&gt; &gt;::HashMap() in main.o
  ld: symbol(s) not found for architecture x86_64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>Here's my clang version info:</p>
  
  <pre><code> Apple LLVM version 7.0.2 (clang-700.1.81)
   Target: x86_64-apple-darwin15.2.0
   Thread model: posix
  </code></pre>
  
  <p>I've searched my way through the web and found a couple of recommendations, for example this one on Reddit:</p>
  
  <p><a href="https://www.reddit.com/r/cpp_questions/comments/3ejfkr/is_c14s_stdshared_timed_mutex_available_on_os_x/" rel="nofollow">https://www.reddit.com/r/cpp_questions/comments/3ejfkr/is_c14s_stdshared_timed_mutex_available_on_os_x/</a>?</p>
  
  <p>This is very close to my problem, I've tried the suggestions, but I´m hoping, that I won´t have to do the manual libc++ download, but could stick with the standard libs shipped with my system.</p>
  
  <p>Thank you!</p>