Add preliminary IEEE 802.11n support into hostapd

Add preliminary IEEE 802.11n support into hostapd

This commit brings in cleaned up version of IEEE 802.11n implementation
from Intel (1). The Intel tarball includes number of other changes, too,
and only the changes specific to IEEE 802.11n are brought in here. In
addition, this does not include all the changes (e.g., some of the
configuration parameters are still missing and driver wrapper changes for
mac80211 were not included).

(1)
http://www.kernel.org/pub/linux/kernel/people/chuyee/wireless/iwl4965_ap/hostap_0_6_0_intel_0.0.13.1.tgz