configure: add empty line after each missing component message

Currently whenever message about missing GMime, Glib or talloc is
printed the message is 2 lines, component info and its http location
in next line. In the future the amount of lines will vary. To ease
reading in these cases newline is added after each message.

configure

@@ -404,17 +404,19 @@ EOF
     if [ $have_gmime -eq 0 ]; then
 	echo "	GMime 2.4 library (including development files such as headers)"
 	echo "	http://spruce.sourceforge.net/gmime/"
+	echo
     fi
     if [ $have_glib -eq 0 ]; then
 	echo "	Glib library >= 2.22 (including development files such as headers)"
 	echo "	http://ftp.gnome.org/pub/gnome/sources/glib/"
+	echo
     fi
     if [ $have_talloc -eq 0 ]; then
 	echo "	The talloc library (including development files such as headers)"
 	echo "	http://talloc.samba.org/"
+	echo
     fi
     cat <<EOF
-
 With any luck, you're using a modern, package-based operating system
 that has all of these packages available in the distribution. In that
 case a simple command will install everything you need. For example: