First set of manpage markup fixes

First set of manpage markup fixes

Enclosed patch fixes inappropriate uses of the .SS macro.  Fuller explanation
in the change comment.

There are other problems in these pages that block lifting to
XML-DocBook, most notably in the command synopses.  They will take
some creativity to fix.  I'm working on it

>From 75745adba4b45b87577b61a2daa886dd444f44da Mon Sep 17 00:00:00 2001
From: "Eric S. Raymond" <esr@thyrsus.com>
Date: Fri, 21 Jun 2013 15:27:38 -0400
Subject: [PATCH] Abolish presentation-level misuse of the .SS macro.

This change fixes most (but not all) fatal errors in attempts to lift
the iproute2 manual pages to XML-DocBook.  Where .SS is still used it
is a real subsection header, not just a way to outdent and bold text.
Presentation-level instances are turned into .TP calls and tables.