doc: mention pg_reload_conf() for reloading the config file

Reported-by: Ian Barwick

Discussion: https://postgr.es/m/538950ec-b86a-1650-6078-beb7091c09c2@2ndquadrant.com

Backpatch-through: 9.4

doc/src/sgml/client-auth.sgml

@@ -650,8 +650,9 @@ hostnogssenc <replaceable>database</replaceable>  <replaceable>user</replaceable
    <systemitem>SIGHUP</systemitem><indexterm><primary>SIGHUP</primary></indexterm>
    signal. If you edit the file on an
    active system, you will need to signal the postmaster
-   (using <literal>pg_ctl reload</literal> or <literal>kill -HUP</literal>) to make it
-   re-read the file.
+   (using <literal>pg_ctl reload</literal>, calling the SQL function
+   <function>pg_reload_conf()</function>, or using <literal>kill
+   -HUP</literal>) to make it re-read the file.
   </para>
 
   <note>
@@ -871,8 +872,9 @@ mymap   /^(.*)@otherdomain\.com$   guest
    <systemitem>SIGHUP</systemitem><indexterm><primary>SIGHUP</primary></indexterm>
    signal. If you edit the file on an
    active system, you will need to signal the postmaster
-   (using <literal>pg_ctl reload</literal> or <literal>kill -HUP</literal>) to make it
-   re-read the file.
+   (using <literal>pg_ctl reload</literal>, calling the SQL function
+   <function>pg_reload_conf()</function>, or using <literal>kill
+   -HUP</literal>) to make it re-read the file.
   </para>
 
   <para>