pg_walsummary: Document --version option

It was working, but it was not shown in the --help output or on the
man page.

doc/src/sgml/ref/pg_walsummary.sgml

@@ -83,6 +83,16 @@ PostgreSQL documentation
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><option>-V</option></term>
+      <term><option>--version</option></term>
+      <listitem>
+       <para>
+        Display version information, then exit.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
        <term><option>-?</option></term>
        <term><option>--help</option></term>

src/bin/pg_walsummary/pg_walsummary.c

@@ -270,6 +270,7 @@ help(const char *progname)
 	printf(_("\nOptions:\n"));
 	printf(_("  -i, --individual          list block numbers individually, not as ranges\n"));
 	printf(_("  -q, --quiet               don't print anything, just parse the files\n"));
+	printf(_("  -V, --version             output version information, then exit\n"));
 	printf(_("  -?, --help                show this help, then exit\n"));
 
 	printf(_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);