Mailing list subscriptions are currently broken

Put notices on each of the mailing list pages indicating that they are
broken, and provide links to the corresponding github issue "new"
pages as an alternative.

Signed-off-by: Jeff Squyres <jeff@squyres.com>

Author: jsquyres

community/lists/hwloc.php

@@ -19,6 +19,16 @@
 
 <p><center><hr width=50%></center>
 
+<h2 align=center><font color=red>NOTE:</font> New subscriptions to
+the mailing lists curently broken.</h2>
+
+<h2 align=center>Please <a
+href="https://github.com/open-mpi/hwloc/issues/new/choose">create a
+GitHub issue with any questions</a> until we can get the mailing lists
+fixed.</h2>
+
+<p><center><hr width=50%></center>
+
 <P>The following lists are available for the <a href="<?php
 print($topdir); ?>/projects/hwloc/">hwloc</a> community:</p>
 

community/lists/mtt.php

@@ -21,6 +21,16 @@
 
 <p><center><hr width=50%></center>
 
+<h2 align=center><font color=red>NOTE:</font> New subscriptions to
+the mailing lists curently broken.</h2>
+
+<h2 align=center>Please <a
+href="https://github.com/open-mpi/mtt/issues/new/choose">create a
+GitHub issue with any questions</a> until we can get the mailing lists
+fixed.</h2>
+
+<p><center><hr width=50%></center>
+
 <P>The following lists are available for the <a href="<?php
 print($topdir); ?>/projects/mtt/">MTT</a> community:</p>
 

community/lists/ompi.php

@@ -26,6 +26,16 @@
 
 <p><center><hr width=50%></center>
 
+<h2 align=center><font color=red>NOTE:</font> New subscriptions to
+the mailing lists curently broken.</h2>
+
+<h2 align=center>Please <a
+href="https://github.com/open-mpi/ompi/issues/new/choose">create a
+GitHub issue with any questions</a> until we can get the mailing lists
+fixed.</h2>
+
+<p><center><hr width=50%></center>
+
 <P>The following lists are available for the Open MPI community:</p>
 
 <P>