CLI server: add regression tests for "Host" header reflection

The server responds with a "Host" header that is copied from the request, add a
test so that when the behavior changes it is visible.

Author: DanielEScherzer

sapi/cli/tests/php_cli_server_023.phpt

@@ -0,0 +1,45 @@
+--TEST--
+Built-in web server reflects arbitrary `Host` headers
+--SKIPIF--
+<?php
+include "skipif.inc";
+?>
+--FILE--
+<?php
+include "php_cli_server.inc";
+php_cli_server_start(<<<'PHP'
+echo "Request headers:\n";
+var_dump(getallheaders());
+PHP
+);
+
+$req = <<<END
+GET / HTTP/1.1
+Host: Foo Bar Baz
+
+
+
+END;
+
+$fp = php_cli_server_connect();
+if (fwrite($fp, $req)) {
+	while (!feof($fp)) {
+		echo fgets($fp);
+	}
+}
+fclose($fp);
+
+?>
+--EXPECTF--
+HTTP/1.1 200 OK
+Host: Foo Bar Baz
+Date: %s
+Connection: close
+X-Powered-By: %s
+Content-type: text/html; charset=UTF-8
+
+Request headers:
+array(1) {
+  ["Host"]=>
+  string(11) "Foo Bar Baz"
+}