title: GNU Autotools, what is "*h.in" files?
body: <p>I am new to autotools, and can't find out where from *.h.in files are created?
  I am trying to create small hello_demo for my library, where I include *.h and use it. <em>make</em> throws me error, that  *h.in not found.</p>
  
  <p>Any guide how to make it proper way, will be very appreciate)</p>