Make download_file_content()/class curl to observe "moved" headers with open_basedir or safe_mode in effect

This was discovered while fixing MDLSITE-1810

Right now, sites with open_basedir and/or safe_mode in effect have one severe limitation in their download_file_content() implementation. They simply are not allowed to follow 30x response headers.

    if (!ini_get('open_basedir') and !ini_get('safe_mode')) {

        // TODO: add version test for '7.10.5'

        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);

        curl_setopt($ch, CURLOPT_MAXREDIRS, 5);

    }

We should take rid of that limitation ASAP, for all supported branches, there are a lot of alternatives out there to "manually" follow them in a transparent way:

• http://php.net/manual/en/function.curl-setopt.php#102121
• https://github.com/kevinsperrine/Wufoo-PHP-API-Wrapper/commit/37a5fdaff5fdb4aae8d5bd5df3a34b7b71d67261

Ciao