Add link to posix.constants.setrlimit page (#4772)

Author: zonuexe

reference/posix/functions/posix-getrlimit.xml

@@ -27,8 +27,10 @@
      <term><parameter>resource</parameter></term>
      <listitem>
       <para>
-       If &null; all resource limits will be fetched.
-       Otherwise, the only limits of the resource type provided will be returned.
+       If &null;, all current resource limits will be returned.
+       Otherwise, specify the
+       <link linkend="posix.constants.setrlimit">resource limit constant</link>
+       to retrieve a specific limit.
       </para>
      </listitem>
     </varlistentry>