hostapd: Add a database of neighboring APs

hostapd: Add a database of neighboring APs

Add a configurable neighbor database that includes the content of
Nighbor Report element, LCI and Location Civic subelements and SSID.

All parameters for a neighbor must be updated at once; Neighbor Report
element and SSID are mandatory, LCI and civic are optional. The age of
LCI is set to the time of neighbor update.

The control interface API is:
SET_NEIGHBOR <BSSID> <ssid=SSID> <nr=data> [lci=<data>] [civic=<data>]

To delete a neighbor use:
REMOVE_NEIGHBOR <BSSID> <SSID>

Signed-off-by: David Spinadel <david.spinadel@intel.com>