title: AX_CXX_COMPILE_STDCXX_11 doesn't work: syntax error near unexpected token `,'
body: <p>Trying to use AX_CXX_COMPILE_STDCXX_11 in my configure.ac file like this:</p>
  
  <pre><code>...
  AX_CXX_COMPILE_STDCXX_11(, optional)
  ...
  </code></pre>
  
  <p>However, results in error:</p>
  
  <pre><code>./configure: line 16126: syntax error near unexpected token `,'
  ./configure: line 16126: `AX_CXX_COMPILE_STDCXX_11(, optional)'
  </code></pre>
  
  <p>I've also placed <a href="http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_cxx_compile_stdcxx_11.m4" rel="nofollow">this file</a> into m4 directory next to configure.ac file and have <code>AC_CONFIG_MACRO_DIR([m4])</code> called in configure.ac in the very beginning.
  Did anyone faced anything like that before?</p>