[Cherrypicking] disable extra protocols to prevent CVE-2013-0249

    There is a buffer overflow in libcurl POP3/SMTP/IMAP.  The workaround is
    simple: disable extra protocols so that they cannot be exploited.  Full
    details here:

      http://curl.haxx.se/docs/adv_20130206.html

    QEMU only cares about HTTP, HTTPS, FTP, FTPS, and TFTP.  I have tested
    that this fix prevents the exploit on my host with
    libcurl-7.27.0-5.fc18.