SCRIPTS: announce-release: place the send command in the mail's header

I'm fed up with having to scroll my terminals trying to look for the
mail send command printed 30 minutes before the release, let's have
it copied into the e-mail template itself, and replace the old headers
that used to be duplicated there and that are not needed anymore.
diff --git a/scripts/announce-release b/scripts/announce-release
index 3e0d1e3..ff32d32 100755
--- a/scripts/announce-release
+++ b/scripts/announce-release
@@ -117,9 +117,12 @@
 	die "$HTML already exists, please remove it."
 fi
 
-(echo "Subject: [ANNOUNCE] haproxy-$NEW"
- echo "To: haproxy@formilux.org"
- echo
+(
+ echo "# Send this using:"
+ echo "#   mutt -i <(tail -n +4 ${OUTPUT##*/}) -s \"[ANNOUNCE] haproxy-$NEW\" haproxy@formilux.org"
+) >> "$OUTPUT"
+
+(echo
  echo "Hi,"
  echo
  echo -n "HAProxy $NEW was released on $DATE. It added "
@@ -210,7 +213,7 @@
 echo "The announce was emitted into file $OUTPUT."
 echo "You can edit it and send it this way :"
 echo
-echo "   mutt -i ${OUTPUT##*/} -s \"[ANNOUNCE] haproxy-$NEW\" haproxy@formilux.org"
+echo "   mutt -i <(tail -n +4 ${OUTPUT##*/}) -s \"[ANNOUNCE] haproxy-$NEW\" haproxy@formilux.org"
 echo
 echo "The HTML block was emitted into $HTML and needs to be finished by hand."
 echo