Fixes for GeoIP support (addresses #538).

- Missing GeoIP databases now generate warnings/errors that go through
  the reporter framework instead of hitting GeoIP's internal use of
  stderr

- lookup_location now just queries for country code if the city database
  was not loaded, which gets rid of invalid database type errors.

- lookup_location now leaves missing fields uninitialized in the
  returned geo_location record value.  Updated existing scripts to
  check for initialized fields in geo_location records before use.

- Fixed support for GeoIP's IPv6 API and databases

scripts/policy/protocols/ssh/geo-data.bro

@@ -33,7 +33,7 @@ event SSH::heuristic_successful_login(c: connection) &priority=5
 	# Add the location data to the SSH record.
 	c$ssh$remote_location = location;
 	
-	if ( location$country_code in watched_countries )
+	if ( location?$country_code && location$country_code in watched_countries )
 		{
 		NOTICE([$note=Login_From_Watched_Country,
 		        $conn=c,