ldap_control_paged_result is deprecated in php 7.4

[xyphoid]

Happened to discover this when loading the /LDAPDebug page on a test site on php 7.4. This is used in LDAPIterator

https://www.php.net/manual/en/migration74.deprecated.php#migration74.deprecated.ldap

This looks annoying to handle because the replacement for this is new behaviour on ldap_search which was added in 7.3. This means that to have code that works on both 7.2 and 7.4 will involve conditional version checking and having both versions - for example see https://tracker.moodle.org/browse/MDL-67118 for the same issue in Moodle.