-Codechange: Do not hardcode the catchment radius of airports, but hold the information in AirportFTAClass
-Fix (r979): The default AI tested possible airport locations with a fixed catchment radius instead of the radius of the to be built airport
The landscaping toolbar can be reached at least as easy directly from the main toolbar.
Further two of the four toolbars uses 'l' as keyboard shortcut for this button, which plain does not work (The letter has to be uppercase).
This was covered by the fact there is a global shortcut 'L' to open the landscaping toolbar, so the individual checks in the four build toolbars were redundant anyway.
