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

autogen.sh

@@ -124,13 +124,23 @@ fi
 echo "Generating configuration files for $package, please wait...."
 
 ACLOCAL_FLAGS="$ACLOCAL_FLAGS -I $PWD/m4"
-if [ -d /usr/local/share/aclocal ]; then
-	ACLOCAL_FLAGS="$ACLOCAL_FLAGS -I /usr/local/share/aclocal"
-fi
 
-# if [ -d "/usr/local/share/`basename $ACLOCAL`" ]; then
-	# ACLOCAL_FLAGS="$ACLOCAL_FLAGS -I /usr/local/share/`basename $ACLOCAL`"
-# fi
+# /usr/share/aclocal is most likely included by default, already...
+ac_local_paths='
+/usr/local/share/aclocal
+/sw/share/aclocal
+/usr/pkg/share/aclocal
+/opt/share/aclocal
+/usr/gnu/share/aclocal
+'
+
+for i in $ac_local_paths; do
+	if test -d "$i"; then
+		ACLOCAL_FLAGS="$ACLOCAL_FLAGS -I $i"
+		# we probably only want one of these...
+		break
+	fi
+done
 
 echo "  $ACLOCAL $ACLOCAL_FLAGS"
 $ACLOCAL $ACLOCAL_FLAGS