RC4: re-add the OpenSSL changes for RC4

looks like they got skipped over when the merge conflict was resolved

phpseclib/Crypt/RC4.php

@@ -135,6 +135,38 @@ class RC4 extends Base
         parent::__construct(Base::MODE_STREAM);
     }
 
+    /**
+     * Test for engine validity
+     *
+     * This is mainly just a wrapper to set things up for Crypt_Base::isValidEngine()
+     *
+     * @see Crypt_Base::Crypt_Base()
+     * @param Integer $engine
+     * @access public
+     * @return Boolean
+     */
+    function isValidEngine($engine)
+    {
+        switch ($engine) {
+            case Base::ENGINE_OPENSSL:
+                switch (strlen($this->key)) {
+                    case 5:
+                        $this->cipher_name_openssl = 'rc4-40';
+                        break;
+                    case 8:
+                        $this->cipher_name_openssl = 'rc4-64';
+                        break;
+                    case 16:
+                        $this->cipher_name_openssl = 'rc4';
+                        break;
+                    default:
+                        return false;
+                }
+        }
+
+        return parent::isValidEngine($engine);
+    }
+
     /**
      * Dummy function.
      *