title: <mqueue.h> and mqd_t on OS X
body: <p>I'm trying to compile a simulation of FreeRTOS on OS X. The simulation code is written for UNIX (POSIX) so I thought that I can comile it on OS X, too.</p>
  
  <p>But I have difficulties with some POSIX threading stuff. XCode can't find the header  and thus the type mqd_t is missing.</p>
  
  <p>What am I doing wrong? Do I need to install some additional libraries? I thoght that OS X is POSIX compatible.</p>
  
  <p>Thx</p>