Doc: fix some description of environment variables with frontend tools

This addresses a couple of issues in the documentation:
- Description of PG_COLOR was missing for some tools (pg_archivecleanup
and pg_test_fsync), while the other descriptions had grammar mistakes.
- pgbench supports more environment variables: PGUSER, PGHOST and
PGPORT.
- vacuumlo, oid2name and pgbench support coloring (HEAD only)

Author: Michael Paquier
Reviewed-by: Fabien Coelho, Daniel Gustafsson, Juan José Santamaría
Flecha
Discussion: https://postgr.es/m/20200304075418.GJ2593@paquier.xyz
Backpatch-through: 12

doc/src/sgml/ref/pgbench.sgml

@@ -883,6 +883,37 @@ pgbench <optional> <replaceable>options</replaceable> </optional> <replaceable>d
   </para>
  </refsect1>
 
+ <refsect1>
+  <title>Environment</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><envar>PGHOST</envar></term>
+    <term><envar>PGPORT</envar></term>
+    <term><envar>PGUSER</envar></term>
+
+    <listitem>
+     <para>
+      Default connection parameters.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist> 
+
+  <para>
+   This utility, like most other <productname>PostgreSQL</productname> utilities,
+   uses the environment variables supported by <application>libpq</application>
+   (see <xref linkend="libpq-envars"/>).
+  </para>
+  
+  <para>
+   The environment variable <envar>PG_COLOR</envar> specifies whether to use
+   color in diagnostic messages. Possible values are
+   <literal>always</literal>, <literal>auto</literal> and
+   <literal>never</literal>.
+  </para>
+ </refsect1>
+ 
  <refsect1>
   <title>Notes</title>