Accept glibtoolize as libtoolize

Of course, we don't really run it, autoreconf does.  We just
err if neither is available.  glibtoolize is the name it is
shipped under on OS X.  Reported by Adam.

autogen.sh

@@ -20,7 +20,7 @@ which pkg-config || {
 }
 
 echo -n "checking for libtoolize... "
-which libtoolize || {
+which glibtoolize libtoolize || {
 	echo "*** No libtoolize (libtool) found, please install it ***"
 	exit 1
 }