libevent : upgrade to 4.0.21

libevent : upgrade to 4.0.21

 - removed libevent-2.0.16_fix_for_x32.patch because the newer version
 contained the changes done by the patch.

 - LICENSE file new checksum caused by :

  old : Copyright (c) 2007-2011 Niels Provos and Nick Mathewson

  new : Copyright (c) 2007-2012 Niels Provos and Nick Mathewson

(From OE-Core rev: eda67a8cb2b2669c12ecda2cf9b00e1001b8c598)

(From OE-Core rev: 830eeee2da5bdea2420a1eac8814e4a51eacbd7a)

Signed-off-by: Andrei Dinu <andrei.adrianx.dinu@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>