use intl's native normalizer_normalize() in case the module is available

lib/base.php

@@ -495,6 +495,9 @@ class OC {
 			require_once $vendorAutoLoad;
 		}
 
+		// initialize intl fallback is necessary
+		\Patchwork\Utf8\Bootup::initIntl();
+
 		if (!defined('PHPUNIT_RUN')) {
 			OC\Log\ErrorHandler::setLogger(OC_Log::$object);
 			if (defined('DEBUG') and DEBUG) {

lib/private/util.php

@@ -1402,14 +1402,12 @@ class OC_Util {
 	 * @return bool|string
 	 */
 	public static function normalizeUnicode($value) {
-		if (class_exists('Patchwork\PHP\Shim\Normalizer')) {
-			$normalizedValue = \Patchwork\PHP\Shim\Normalizer::normalize($value);
-			if ($normalizedValue === false) {
+		$normalizedValue = normalizer_normalize($value);
+		if ($normalizedValue === null || $normalizedValue === false) {
 			\OC_Log::write('core', 'normalizing failed for "' . $value . '"', \OC_Log::WARN);
 		} else {
 			$value = $normalizedValue;
 		}
-		}
 
 		return $value;
 	}