title: Using the pkg-config macro PKG_CHECK_MODULES failing
body: <p>I'm sure this is a fairly simple problem. I have a very simple configure.ac file which I am using to just learn how autoconf &amp; pkg-config work together. The <code>confgure.ac</code> file looks like:</p>
  
  <pre><code>AC_PREREQ(2.61)
  AC_INIT(autoconf_test, 1.0, nowhere@dev.null)
  
  PKG_CHECK_MODULES(libusbmuxd, libusbmuxd &gt;= 0.1.4)
  </code></pre>
  
  <p>I can then execute autoconf from the command line and it does produce a configure script. However, when I run the configure script, I get the following error:</p>
  
  <pre><code>./configure: line 1618: syntax error near unexpected token `libusbmuxd,'
  ./configure: line 1618: `PKG_CHECK_MODULES(libusbmuxd, libusbmuxd &gt;= 0.1.4)'
  </code></pre>
  
  <p>If I use the pkg-config program from the command line to check to see whether it can find this library, it succeeds.</p>
  
  <pre><code>/usr/lib/pkgconfig $pkg-config --libs --cflags --modversion libusbmuxd
  
  1.0.7
  -I/usr/local/Cellar/usbmuxd/1.0.7/include  -L/usr/local/Cellar/usbmuxd/1.0.7/lib -lusbmuxd  
  </code></pre>
  
  <p>So, it seems clear that for some reason the <code>PGK_CHECK_MODULE</code> macro cannot be located and I am not sure why.</p>
  
  <p>This probably isn't OS specific, but I am using Mac OS X 10.6.8.</p>