Enable allowing/disallowing supply to a station, per cargo

Ctrl-click station cargo rating

src/command_type.h

@@ -289,6 +289,7 @@ enum Commands {
 	CMD_RENAME_PRESIDENT,             ///< change the president name
 	CMD_RENAME_STATION,               ///< rename a station
 	CMD_RENAME_DEPOT,                 ///< rename a depot
+	CMD_SET_STATION_CARGO_ALLOWED_SUPPLY, ///< set station cargo allowed supply
 
 	CMD_PLACE_SIGN,                   ///< place a sign
 	CMD_RENAME_SIGN,                  ///< rename a sign