fixed microtime not being numeric

Author: driehle

src/Md5Crypt/Md5Crypt.php

@@ -83,7 +83,7 @@ public static function unix($pw, $salt = null, $Magic = '$1$')
             $salt = substr($parts[0], 0, 8);
         } else {
             $salt = '';
-            mt_srand((float) (microtime() * 10000000));
+            mt_srand((float) (microtime(true) * 10000000));
 
             while (strlen($salt) < 8) {
                 $salt .= $itoa64[mt_rand(0, strlen($itoa64) - 1)];