Update spread to version 4.2.

* Use a hack to work around the download form on the spread website by passing the form fields as GET parameters in the download URL.
* Add a more or less useful test for the package by calling spuser which fortunately exits with 0 even if no connection can be established.
* Fix errors found by brew audit.

I don't know if the max messages patch is still required with 4.2.
merged patch 678c0ed