title: what does it mean? configure.ac: warning: missing AC_CHECK_FUNCS(gettimeofday)
body: <p>I m learning the process of autotools, and when i run autoscan after introducing few functions example </p>
  
  <pre><code> gettimeofday().
  </code></pre>
  
  <p>I am not able to associate the below statement into meaningful? can you explain what it tells?</p>
  
  <pre><code>configure.ac: warning: missing AC_CHECK_FUNCS(gettimeofday)
  </code></pre>