doc: Update example version numbers in pg_upgrade documentation

The exact numbers don't matter, since they are examples, but it was
looking quite dated.

For the target version, we now automatically substitute the current
major version.  The updated example source version should be good for a
couple of years.

doc/src/sgml/ref/pgupgrade.sgml

@@ -38,9 +38,9 @@
   <application>pg_upgrade</> (formerly called <application>pg_migrator</>) allows data
   stored in <productname>PostgreSQL</> data files to be upgraded to a later <productname>PostgreSQL</>
   major version without the data dump/reload typically required for
-  major version upgrades, e.g. from 8.4.7 to the current major release
+  major version upgrades, e.g. from 9.6.3 to the current major release
   of <productname>PostgreSQL</>.  It is not required for minor version upgrades, e.g. from
-  9.0.1 to 9.0.4.
+  9.6.2 to 9.6.3.
  </para>
 
  <para>
@@ -66,7 +66,7 @@
 
   <para>
    pg_upgrade supports upgrades from 8.4.X and later to the current
-   major release of <productname>PostgreSQL</>, including snapshot and alpha releases.
+   major release of <productname>PostgreSQL</>, including snapshot and beta releases.
   </para>
  </refsect1>
 
@@ -207,7 +207,7 @@
 
     <para>
      If you are using a version-specific installation directory, e.g.
-     <filename>/opt/PostgreSQL/9.1</>, you do not need to move the old cluster. The
+     <filename>/opt/PostgreSQL/&majorversion;</>, you do not need to move the old cluster. The
      graphical installers all use version-specific installation directories.
     </para>
 
@@ -298,15 +298,15 @@ make prefix=/usr/local/pgsql.new install
      Make sure both database servers are stopped using, on Unix, e.g.:
 
 <programlisting>
-pg_ctl -D /opt/PostgreSQL/8.4 stop
-pg_ctl -D /opt/PostgreSQL/9.0 stop
+pg_ctl -D /opt/PostgreSQL/9.6 stop
+pg_ctl -D /opt/PostgreSQL/&majorversion; stop
 </programlisting>
 
      or on Windows, using the proper service names:
 
 <programlisting>
-NET STOP postgresql-8.4
-NET STOP postgresql-9.0
+NET STOP postgresql-9.6
+NET STOP postgresql-&majorversion;
 </programlisting>
     </para>
 
@@ -366,17 +366,17 @@ NET STOP postgresql-9.0
 
 <programlisting>
 RUNAS /USER:postgres "CMD.EXE"
-SET PATH=%PATH%;C:\Program Files\PostgreSQL\9.0\bin;
+SET PATH=%PATH%;C:\Program Files\PostgreSQL\&majorversion;\bin;
 </programlisting>
 
      and then run <application>pg_upgrade</> with quoted directories, e.g.:
 
 <programlisting>
 pg_upgrade.exe
-        --old-datadir "C:/Program Files/PostgreSQL/8.4/data"
-        --new-datadir "C:/Program Files/PostgreSQL/9.0/data"
-        --old-bindir "C:/Program Files/PostgreSQL/8.4/bin"
-        --new-bindir "C:/Program Files/PostgreSQL/9.0/bin"
+        --old-datadir "C:/Program Files/PostgreSQL/9.6/data"
+        --new-datadir "C:/Program Files/PostgreSQL/&majorversion;/data"
+        --old-bindir "C:/Program Files/PostgreSQL/9.6/bin"
+        --new-bindir "C:/Program Files/PostgreSQL/&majorversion;/bin"
 </programlisting>
 
      Once started, <command>pg_upgrade</> will verify the two clusters are compatible