configure.ac: Move libao to Audio Output Plugins (nonstreaming), add header.

configure.ac

@@ -897,9 +897,7 @@ fi
 
 AM_CONDITIONAL(HAVE_JACK, test x$enable_jack = xyes)
 
-
-
-
+dnl ---------------------------------- libao ----------------------------------
 MPD_AUTO_PKG(ao, AO, [ao],
 	[libao output plugin], [libao not found])
 if test x$enable_ao = xyes; then
@@ -908,6 +906,8 @@ fi
 
 AM_CONDITIONAL(HAVE_AO, test x$enable_ao = xyes)
 
+
+
 if test x$enable_pipe_output = xyes; then
 	AC_DEFINE([ENABLE_PIPE_OUTPUT], 1,
 		[Define to enable support for writing audio to a pipe])