Enable "native_constant_invocation" CS rule

Author: nicolas-grekas

Adapter/ExtLdap/Adapter.php

@@ -72,7 +72,7 @@ public function escape($subject, $ignore = '', $flags = 0)
         $value = ldap_escape($subject, $ignore, $flags);
 
         // Per RFC 4514, leading/trailing spaces should be encoded in DNs, as well as carriage returns.
-        if ((int) $flags & LDAP_ESCAPE_DN) {
+        if ((int) $flags & \LDAP_ESCAPE_DN) {
             if (!empty($value) && ' ' === $value[0]) {
                 $value = '\\20'.substr($value, 1);
             }

LdapClient.php

@@ -11,7 +11,7 @@
 
 namespace Symfony\Component\Ldap;
 
-@trigger_error('The '.__NAMESPACE__.'\LdapClient class is deprecated since Symfony 3.1 and will be removed in 4.0. Use the Ldap class directly instead.', E_USER_DEPRECATED);
+@trigger_error('The '.__NAMESPACE__.'\LdapClient class is deprecated since Symfony 3.1 and will be removed in 4.0. Use the Ldap class directly instead.', \E_USER_DEPRECATED);
 
 /**
  * @author Grégoire Pineau <lyrixx@lyrixx.info>
@@ -60,7 +60,7 @@ public function getEntryManager()
      */
     public function find($dn, $query, $filter = '*')
     {
-        @trigger_error('The "find" method is deprecated since Symfony 3.1 and will be removed in 4.0. Use the "query" method instead.', E_USER_DEPRECATED);
+        @trigger_error('The "find" method is deprecated since Symfony 3.1 and will be removed in 4.0. Use the "query" method instead.', \E_USER_DEPRECATED);
 
         $query = $this->ldap->query($dn, $query, ['filter' => $filter]);
         $entries = $query->execute();