gnutls: update to 3.2.13

Removes not needed or already merged patches.

Removes unused configure flags.
Tells gnutls to use the included libopts.

Removes libextra (not needed since 3.0.5).

Signed-off-by: Valentin Popa <valentin.popa@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>