/*
   -4 -3 -2 -1 00 01 02 03 04 05 ->>> x
-4 xx xx xx xx xx xx xx xx xx xx
-3 xx                         xx
-2 xx                         xx
-1 xx       xx xx xx xx       xx
00 xx       xx 18 1A xx       xx
01 xx       xx 18 1B xx       xx
02 xx       xx 19 1C xx       xx
03 xx       xx xx xx xx       xx
04 xx                         xx
05 xx                         xx
06 xx xx xx xx xx xx xx xx xx xx

^
^
|
y

switch (FEAT_INDUSTRIES, SELF, oil_rig_location_callback, industry_distance(INDUSTRYTYPE_OIL_RIG, -1) ) {
 0..6: CB_RESULT_LOCATION_DISALLOW;
 CB_RESULT_LOCATION_ALLOW;
}
*/