doc: add commas after 'i.e.' and 'e.g.'

This follows the American format,
https://jakubmarian.com/comma-after-i-e-and-e-g/. There is no intention
of requiring this format for future text, but making existing text
consistent every few years makes sense.

Discussion: https://postgr.es/m/20200825183619.GA22369@momjian.us

Backpatch-through: 9.5

doc/src/sgml/ref/pgupgrade.sgml

@@ -41,8 +41,8 @@ PostgreSQL documentation
   <application>pg_upgrade</application> (formerly called <application>pg_migrator</application>) allows data
   stored in <productname>PostgreSQL</productname> data files to be upgraded to a later <productname>PostgreSQL</productname>
   major version without the data dump/reload typically required for
-  major version upgrades, e.g. from 9.5.8 to 9.6.4 or from 10.7 to 11.2.
-  It is not required for minor version upgrades, e.g. from 9.6.2 to 9.6.3
+  major version upgrades, e.g., from 9.5.8 to 9.6.4 or from 10.7 to 11.2.
+  It is not required for minor version upgrades, e.g., from 9.6.2 to 9.6.3
   or from 10.1 to 10.2.
  </para>
 
@@ -60,7 +60,7 @@ PostgreSQL documentation
 
  <para>
   <application>pg_upgrade</application> does its best to
-  make sure the old and new clusters are binary-compatible, e.g.  by
+  make sure the old and new clusters are binary-compatible, e.g.,  by
   checking for compatible compile-time settings, including 32/64-bit
   binaries.  It is important that
   any external modules are also binary compatible, though this cannot
@@ -239,13 +239,13 @@ PostgreSQL documentation
     <title>Optionally move the old cluster</title>
 
     <para>
-     If you are using a version-specific installation directory, e.g.
+     If you are using a version-specific installation directory, e.g.,
      <filename>/opt/PostgreSQL/&majorversion;</filename>, you do not need to move the old cluster. The
      graphical installers all use version-specific installation directories.
     </para>
 
     <para>
-     If your installation directory is not version-specific, e.g.
+     If your installation directory is not version-specific, e.g.,
      <filename>/usr/local/pgsql</filename>, it is necessary to move the current PostgreSQL install
      directory so it does not interfere with the new <productname>PostgreSQL</productname> installation.
      Once the current <productname>PostgreSQL</productname> server is shut down, it is safe to rename the
@@ -303,9 +303,9 @@ make prefix=/usr/local/pgsql.new install
 
     <para>
      Install any custom shared object files (or DLLs) used by the old cluster
-     into the new cluster, e.g. <filename>pgcrypto.so</filename>,
+     into the new cluster, e.g., <filename>pgcrypto.so</filename>,
      whether they are from <filename>contrib</filename>
-     or some other source. Do not install the schema definitions, e.g.
+     or some other source. Do not install the schema definitions, e.g.,
      <command>CREATE EXTENSION pgcrypto</command>, because these will be upgraded
      from the old cluster.
      Also, any custom full text search files (dictionary, synonym,
@@ -516,7 +516,7 @@ pg_upgrade.exe
 
       <para>
        Save any configuration files from the old standbys' configuration
-       directories you need to keep, e.g.  <filename>postgresql.conf</filename>
+       directories you need to keep, e.g.,  <filename>postgresql.conf</filename>
        (and any files included by it), <filename>postgresql.auto.conf</filename>,
        <literal>pg_hba.conf</literal>, because these will be overwritten
        or removed in the next step.
@@ -543,7 +543,7 @@ rsync --archive --delete --hard-links --size-only --no-inc-recursive old_cluster
        on the standby.  The directory structure under the specified
        directories on the primary and standbys must match.  Consult the
        <application>rsync</application> manual page for details on specifying the
-       remote directory, e.g.
+       remote directory, e.g.,
 
 <programlisting>
 rsync --archive --delete --hard-links --size-only --no-inc-recursive /opt/PostgreSQL/9.5 \
@@ -669,7 +669,7 @@ psql --username=postgres --file=script.sql postgres
      <command>pg_upgrade</command> completes. (Automatic deletion is not
      possible if you have user-defined tablespaces inside the old data
      directory.)  You can also delete the old installation directories
-     (e.g. <filename>bin</filename>, <filename>share</filename>).
+     (e.g., <filename>bin</filename>, <filename>share</filename>).
     </para>
    </step>
 
@@ -793,7 +793,7 @@ psql --username=postgres --file=script.sql postgres
    If you are upgrading a pre-<productname>PostgreSQL</productname> 9.2 cluster
    that uses a configuration-file-only directory, you must pass the
    real data directory location to <application>pg_upgrade</application>, and
-   pass the configuration directory location to the server, e.g.
+   pass the configuration directory location to the server, e.g.,
    <literal>-d /real-data-directory -o '-D /configuration-directory'</literal>.
   </para>
 
@@ -815,7 +815,7 @@ psql --username=postgres --file=script.sql postgres
    copy with any changes to make it consistent.  (<option>--checksum</option>
    is necessary because <command>rsync</command> only has file modification-time
    granularity of one second.)  You might want to exclude some
-   files, e.g. <filename>postmaster.pid</filename>, as documented in <xref
+   files, e.g., <filename>postmaster.pid</filename>, as documented in <xref
    linkend="backup-lowlevel-base-backup"/>.  If your file system supports
    file system snapshots or copy-on-write file copies, you can use that
    to make a backup of the old cluster and tablespaces, though the snapshot