Merge branch '6.4' into 7.2

* 6.4:
  properly skip signal test if the pcntl extension is not installed
  ensure that all supported e-mail validation modes can be configured
  [Security][LoginLink] Throw InvalidLoginLinkException on invalid parameters
  don't hardcode OS-depending constant values

Author: xabbuh

Tests/SignalRegistry/SignalMapTest.php

@@ -18,15 +18,13 @@ class SignalMapTest extends TestCase
 {
     /**
      * @requires extension pcntl
-     *
-     * @testWith [2, "SIGINT"]
-     *           [9, "SIGKILL"]
-     *           [15, "SIGTERM"]
-     *           [31, "SIGSYS"]
      */
-    public function testSignalExists(int $signal, string $expected)
+    public function testSignalExists()
     {
-        $this->assertSame($expected, SignalMap::getSignalName($signal));
+        $this->assertSame('SIGINT', SignalMap::getSignalName(\SIGINT));
+        $this->assertSame('SIGKILL', SignalMap::getSignalName(\SIGKILL));
+        $this->assertSame('SIGTERM', SignalMap::getSignalName(\SIGTERM));
+        $this->assertSame('SIGSYS', SignalMap::getSignalName(\SIGSYS));
     }
 
     public function testSignalDoesNotExist()