support libressl

closes #5917

src/Composer/Repository/PlatformRepository.php

@@ -162,7 +162,7 @@ class PlatformRepository extends ArrayRepository
                     break;
 
                 case 'openssl':
-                    $prettyVersion = preg_replace_callback('{^(?:OpenSSL\s*)?([0-9.]+)([a-z]*).*}', function ($match) {
+                    $prettyVersion = preg_replace_callback('{^(?:OpenSSL|LibreSSL)?\s*([0-9.]+)([a-z]*).*}i', function ($match) {
                         if (empty($match[2])) {
                             return $match[1];
                         }