package/libplist: security bump to version 2.0.0

package/libplist: security bump to version 2.0.0

Release notes:
https://github.com/libimobiledevice/libplist/blob/master/NEWS

This version bump fixes
  * CVE-2017-6440
  * CVE-2017-6439
  * CVE-2017-6438
  * CVE-2017-6437
  * CVE-2017-6436
  * CVE-2017-6435
  * CVE-2017-5836
  * CVE-2017-5835
  * CVE-2017-5834
  * CVE-2017-5545
  * CVE-2017-5209
... and several others that didn't receive any CVE (yet).

The dependency to libxml2 was removed.
Autoreconf is not needed anymore, the upstream tarball includes a
configure script.

[Peter: also drop host-pkgconf dependency, only used for cython]
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>