[wwwdocs] about.html - simplify, update, add a bit

[Gerald Pfeifer]

I promised Martin to look into adding more information to
gcc.gnu.org/about.html for new contributors.

This isn't the actual meat, but a number of changes I found
while preparing for that.

Applied (last weekend actually).

Gerald

Split a long sentence.  Adjust the intro.  Add a note to add 
[wwwdocs] to mail subjects.  Streamline notes how to check-in.

Index: about.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/about.html,v
retrieving revision 1.27
diff -u -r1.27 about.html
--- about.html	2 Feb 2017 21:37:32 -0000	1.27
+++ about.html	6 May 2018 14:27:42 -0000
@@ -11,19 +11,20 @@
 <p>These pages are maintained by the GCC team and it's easy to
 <a href="contribute.html#webchanges">contribute</a>.</p>
 
-<p>The web effort was originally led by Jeff Law.  For the last decade
-or so Gerald Pfeifer has been leading the effort, but there are
+<p>The web effort was originally led by Jeff Law.  For the last two
+decades or so Gerald Pfeifer has been leading the effort, but there are
 many
 <a href="https://gcc.gnu.org/onlinedocs/gcc/Contributors.html">contributors
 </a>.</p>
 
 <p>The web pages are under <a href="#cvs">CVS control</a>.
 The pages on gcc.gnu.org are updated directly after a
-change has been committed; www.gnu.org is updated once a day at 4:00 -0700
+change has been committed. www.gnu.org is updated once a day at 4:00 -0700
 (PDT).</p>
 
 <p>Please send feedback, problem reports and patches to our
-<a href="lists.html">mailing lists</a>.
+<a href="lists.html">mailing lists</a>, ideally putting the
+string "[wwwdocs]" at the beginning of the mail subject.
 </p>
 
 
@@ -62,10 +63,8 @@
 
 <h3>Checking in a change</h3>
 
-<p>The following is a very quick overview of how
-to check in a change.  We recommend you list files explicitly
-to avoid accidental checkins and prefer that each checkin be of a
-complete, single logical change.</p>
+<p>We recommend you list files explicitly to avoid accidental checkins
+and prefer that each checkin be of a complete, single logical change.</p>
 
 <ol>
 <li>Sync your sources with the master repository via "<code>cvs