doc: Add description for PGSSLCRLDIR
This was missing in the section dedicated to the supported environment
variables of libpq.  Oversight in
Discussion:
@@ -7836,6 +7836,16 @@ myEventProc(PGEventId evtId, void *evtInfo, void *passThrough)
</para>
</listitem>
+ <listitem>
+ <para>
+ <indexterm>
+ <primary><envar>PGSSLCRLDIR</envar></primary>
+ </indexterm>
+ <envar>PGSSLCRLDIR</envar> behaves the same as the <xref
+ linkend="libpq-connect-sslcrldir"/> connection parameter.
+ </para>
+ </listitem>
+
<listitem>
<para>
<indexterm>
