ext/ldap: Sync ldap_exop() signature to match stubs (#5623)

The return type is documented as mixed but ldap_exop() returns
LDAP\Result|bool, and the request_data and controls parameters are
nullable (?string and ?array).

Author: lacatoire

reference/ldap/functions/ldap-exop.xml

@@ -9,11 +9,11 @@
  <refsect1 role="description">
   &reftitle.description;
   <methodsynopsis>
-   <type>mixed</type><methodname>ldap_exop</methodname>
+   <type class="union"><type>LDAP\Result</type><type>bool</type></type><methodname>ldap_exop</methodname>
    <methodparam><type>LDAP\Connection</type><parameter>ldap</parameter></methodparam>
    <methodparam><type>string</type><parameter>request_oid</parameter></methodparam>
-   <methodparam choice="opt"><type>string</type><parameter>request_data</parameter><initializer>&null;</initializer></methodparam>
-   <methodparam choice="opt"><type>array</type><parameter>controls</parameter><initializer>&null;</initializer></methodparam>
+   <methodparam choice="opt"><type class="union"><type>string</type><type>null</type></type><parameter>request_data</parameter><initializer>&null;</initializer></methodparam>
+   <methodparam choice="opt"><type class="union"><type>array</type><type>null</type></type><parameter>controls</parameter><initializer>&null;</initializer></methodparam>
    <methodparam choice="opt"><type>string</type><parameter role="reference">response_data</parameter></methodparam>
    <methodparam choice="opt"><type>string</type><parameter role="reference">response_oid</parameter></methodparam>
   </methodsynopsis>