Some more autotools fixes/hacks/workarounds

autogen.sh:
Detect more strange paths for aclocal on different
packaging systems.  This should help encourage more
people to run svn code on their systems.

configure.ac:
Tested on FreeBSD (6.1).  Darwin, OpenBSD, NetBSD info
gleaned off the Makefile distributed with git.

m4/shout.m4:
The Shout 2.2 port on a FreeBSD 6.1 machine seemed
problematic when it's compiled against pthreads, so this is
a gross hack to force -lpthread on it

git-svn-id: https://svn.musicpd.org/mpd/trunk@4390 09075e82-0dd4-0310-85a5-a0d7c8717e4f

m4/shout.m4

@@ -53,6 +53,17 @@ then
   ac_save_CPPFLAGS="$CPPFLAGS"
   ac_save_CFLAGS="$CFLAGS"
   ac_save_LIBS="$LIBS"
+
+  # freebsd 6.1 + shout 2.2 port seems to leave pthread out
+  case "$host_os" in
+  freebsd*)
+	case "$SHOUT_CFLAGS$SHOUT_CPPFLAGS" in
+	*-D_THREAD_SAFE*)
+		SHOUT_LIBS="$SHOUT_LIBS -lpthread"
+		;;
+	esac
+	;;
+  esac
   CPPFLAGS="$CPPFLAGS $SHOUT_CPPFLAGS"
   CFLAGS="$CFLAGS $SHOUT_CFLAGS"
   LIBS="$SHOUT_LIBS $LIBS"